Civil Rights Act of 1964, 42 U.S.C. §§ 2000e–2(a)(1) to (2) (2012).

Bd. of Educ., Island Trees Union Free Sch. Dist. No. 26 v. Pico, 457 U.S. 853, 871-72 (1982).

Comm’r. v. Duberstein, 363 U.S. 278, 285-87 (1960) (quoting Comm’r. v. LoBue, 351 U.S. 243, 246 (1956)).

See 2 James Fitzjames Stephen, A History of the Criminal Law of England 121 (London, MacMillan & Co. 1883) (“[A] man’s motives for any given act . . . are always mixed.”); see also Martin J. Katz, The Fundamental Incoherence of Title VII: Making Sense of Causation in Disparate Treatment Law, 94 Geo. L.J. 489, 491 (2006) (asserting that mixed motives employment discrimination cases are “likely the lion’s share of cases”).

See Linda Hamilton Krieger, The Content of Our Categories: A Cognitive Bias Approach to Discrimination and Equal Employment Opportunity, 47 Stan. L. Rev. 1161, 1164-65 (1995) (discussing cognitive bias as a source of discrimination); Charles R. Lawrence III, The Id, the Ego, and Equal Protection: Reckoning with Unconscious Racism, 39 Stan. L. Rev. 317, 322-23 (1987) (discussing unconscious motivations in racially discriminatory actions).

Staub v. Proctor Hosp., 562 U.S. 411, 419-20 (2011) (considering whether the bias of an employee is attributable to his employer, Proctor Hospital).

See, e.g., United States v. O’Brien, 391 U.S. 367, 384 (1968) (declining to consider whether the motives of several congressmen can be attributed to the entire body). Compare Kenneth A. Shepsle, Congress Is a “They,” Not an “It”: Legislative Intent as Oxymoron, 12 Int’l Rev. L. & Econ. 239, 244-45 (1992) (arguing against the sensibility of an intent inquiry for a collective body), with Richard H. Fallon, Jr., Constitutionally Forbidden Legislative Intent, 130 Harv. L. Rev. 523, 537-41 (2016) (articulating three seemingly feasible intent inquiries applicable to Congress).

Perry v. Brown, 671 F.3d 1052, 1093 (9th Cir. 2012) (scrutinizing the purpose motivating Proposition 8, a ballot initiative to bar same-sex couples from marrying), vacated on other grounds and remanded sub nom. Hollingsworth v. Perry, 133 S. Ct. 2652 (2013).

See infra note 42 and accompanying text; see also infra Section III.A.2.

See infra note 183.

See infra notes 105-109 and accompanying text.

See infra note 42 and accompanying text; see also infra Section III.A.2.

See infra note 100 and accompanying text.

Walter J. Blum, Motive, Intent, and Purpose in Federal Income Taxation, 34 U. Chi. L. Rev. 485, 507 (1967). The absence of legislative guidance is ironic to those who have argued that legislatures are better positioned than courts to “attend to motives.” E.g., Antony Duff, Principle and Contraction in Criminal Law: Motives and Criminal Liability, in Philosophy and the Criminal Law: Principle and Critique 156, 177-78 (Antony Duff ed., 1998).

For example, when prosecutors are alleged to have unconstitutionally struck jurors for their race or gender under Batson v. Kentucky, 476 U.S. 79 (1986), there are now three different rules for evaluating mixed motives. Compare Cook v. LaMarque, 593 F.3d 810, 815 (9th Cir. 2010) (“motivated in substantial part” standard), with Howard v. Senkowski, 986 F.2d 24, 30 (2d Cir. 1993) (but-for standard), and State v. Shuler, 545 S.E.2d 805, 811 (S.C. 2001) (per se standard). Prior to Price Waterhouse v. Hopkins, 490 U.S. 228 (1989), five different approaches divided the circuits on Title VII identity discrimination. See Berl v. Cty. of Westchester, 849 F.2d 712, 714-15 (2d Cir. 1988) (substantial part test, with the burden shifted to the defendant); Terbovitz v. Fiscal Court, 825 F.2d 111, 115 (6th Cir. 1987) (“motivating factor” test, with the burden shifted to the defendant); McQuillen v. Wis. Educ. Ass’n Council, 830 F.2d 659, 664-65 (7th Cir. 1987) (but-for test); Bibbs v. Block, 778 F.2d 1318, 1323-24 (8th Cir. 1985) (en banc) (“discernible factor” test, with the burden shifted to the defendant in order to limit the scale and scope of damages); Fadhl v. City & Cty. of S.F., 804 F.2d 1097, 1099 (9th Cir. 1986) (but-for test, with the burden shifted to the defendants); Toney v. Block, 705 F.2d 1364, 1366 (D.C. Cir. 1983) (same as Fadhl).

There were four cases from 2009 to 2016, and there have been seventeen cases since 1989. This figure excludes the countless instances in which the Court acknowledges a mixed motives circuit split but then declines to address it. See, e.g., Foster v. Chatman, 136 S. Ct. 1737, 1754 n.6 (2016) (acknowledging but declining to decide the question of whether discriminatory intent underlying a strike was nevertheless not “determinative” to the prosecution’s decision to exercise a strike); Snyder v. Louisiana, 552 U.S. 472, 478 (2007) (same).

E.g., Price Waterhouse, 490 U.S. 228.

See, e.g., Chang v. INS, 119 F.3d 1055, 1065 (3d Cir. 1997) (adopting an “at least in part” standard without any consideration of other possible motive standards); see also William A. Klein, The Deductibility of Transportation Expenses of a Combination Business and Pleasure Trip—A Conceptual Analysis, 18 Stan. L. Rev. 1099, 1105 (1966) (“[C]ourts and commentators seem to treat the primary purpose test as a matter of natural law rather than legislative command; at least I have come across no case or commentary in which either its soundness or its statutory basis has been closely examined.”); cf. Niblock v. Comm’r, 417 F.2d 1185, 1187 (7th Cir. 1969) (adopting a predominant purpose—or “dominant and primary motivation”—test to advance “certainty” without explaining why this test is conducive to that goal).

See, e.g., Batson, 476 U.S. at 94 n.18 (drawing on employment discrimination to inform jury selection). See generally Russell D. Covey, The Unbearable Lightness of Batson: Mixed Motives and Discrimination in Jury Selection, 66 Md. L. Rev. 279, 295 (2007) (discussing the influence of the Supreme Court’s Title VII jurisprudence upon jury selection cases).

See, e.g., SEC v. Masri, 523 F. Supp. 2d 361, 371-72 (S.D.N.Y. 2007) (endorsing a but-for standard after rejecting only one other standard); cf. Palmer v. Thompson, 403 U.S. 217, 224-25 (1971) (rejecting all motive analysis because of problems with two motive tests, without considering other possible tests, such as the but-for test).

Even thoughtful commentaries manage to forget salient tests.E.g., Paul J. Gudel, Beyond Causation: The Interpretation of Action and the Mixed Motives Problem in Employment Discrimination Law, 70 Tex. L. Rev. 17 (1991) (listing five options, but neglecting the Primary Motive standard); Katz, supra note 4, at 499 (listing six causal concepts, but neglecting Primary Motive).

See infra Appendix B.

See infra Section I.B. But see Mark C. Weber, Beyond Price Waterhouse v. Hopkins: A New Approach to Mixed Motive Discrimination, 68 N.C. L. Rev. 495 (1990) (comparing employment to intentional interference with contractual relations, malicious prosecution, defamation, retaliatory eviction, and concurrent loss tort and contracts cases).

One longstanding debate concerns whether the criminal law does and should care about motives. Compare Jerome Hall, General Principles of Criminal Law 8 (2d ed. 1960) (arguing against motives analysis), with Douglas N. Husak, Philosophy of Criminal Law 144 (1987) (arguing in favor of motives analysis). This debate has played out with renewed vigor with respect to motive-based sentencing enhancements for bias and hate crimes. Compare Anthony M. Dillof, Punishing Bias: An Examination of the Theoretical Foundations of Bias Crime Statutes, 91 Nw. U. L. Rev. 1015 (1997) (arguing against motives analysis), and Susan Gellman, Sticks and Stones Can Put You in Jail, But Can Words Increase Your Sentence? Constitutional and Policy Dilemmas of Ethnic Intimidation Laws, 39 UCLA L. Rev. 333 (1991) (arguing against criminal ethnic intimidation laws), and Heidi M. Hurd & Michael S. Moore, Punishing Hatred and Prejudice, 56 Stan. L. Rev. 1081 (2004) (critiquing justifications of hate and bias crime legislation), with Carissa Byrne Hessick, Motive’s Role in Criminal Punishment, 80 S. Cal. L. Rev. 89 (2006) (proposing expanded role for motive in criminal sentencing), and Laurence H. Tribe, The Mystery of Motive, Private and Public: Some Notes Inspired by the Problems of Hate Crime and Animal Sacrifice, 1993 Sup. Ct. Rev. 1, 7 (defending hate crime legislation).

Similar questions arise in private law, which is frequently thought to disregard motive. See, e.g., Nadav Shoked, Two Hundred Years of Spite, 110 Nw. U. L. Rev. 357, 360 (2016) (arguing that property law does not and should not use motive analysis); see also J.B. Ames, How Far an Act May Be a Tort Because of the Wrongful Motive of the Actor, 18 Harv. L. Rev. 411 (1905) (arguing that tort law does and should incorporate motives analysis). But see Thomas M. Cooley, A Treatise on The Law of Torts or the Wrongs Which Arise Independent of Contract 690 (1880) (“Malicious motives make a bad act worse, but they cannot make that a wrong which in its own essence is lawful.”).

Another area of deep controversy concerns the relevance of legislators’ motives for the purposes of judicial review of a statute. See Paul Brest, Palmer v. Thompson: An Approach to the Problem of Unconstitutional Legislative Motive, 1971 Sup. Ct. Rev. 95 (defending motive-based scrutiny); accord Elena Kagan, Private Speech, Public Purpose: The Role of Governmental Motive in First Amendment Doctrine, 63 U. Chi. L. Rev. 413 (1996). Compare United States v. O’Brien, 391 U.S. 367, 383-84 (1968) (asserting broadly that a law’s constitutionality does not depend on the motive that led Congress to enact it), with Wallace v. Jaffree, 472 U.S. 38, 55-57 (1985) (holding a moment of silence law unconstitutional because the Alabama legislature’s motive was to further religion and return prayer to the public schools).

Cf. Wesley Newcomb Hohfeld, Fundamental Legal Concepts as Applied in Judicial Reasoning, 26 Yale L.J. 710, 710-11 (1917) (“The great practical importance of accurate thought and precise expression as regards basic legal ideas and their embodiment in a terminology not calculated to mislead is not always fully realized . . . [even by] many an experienced lawyer . . . .”).

Klein, supra note 18, at 1108 (“Part of the problem is attributable to the deficiencies of our means of communication about common mental phenomena.”).

Crittenden v. Calderon, No. CIV-S-95-1957, 2011 WL 2619097, at *26 (E.D. Cal. June 30, 2011). This passage demonstrates both the challenge of categorizing motives, as well as the risk of muddling motive-standard with standard of proof.

See, e.g., Jessica M. Scales, Tipping the Balance Back: An Argument for the Mixed Motive Theory Under the ADEA, 30 St. Louis U. Pub. L. Rev. 229, 258 (2010) (conflating sole motive, but-for motive, and a “defining” factor analysis).

See, e.g., Hunter v. Underwood, 471 U.S. 222, 232 (1985) (endorsing one test and then applying a different one); infra Section I.A. (discussing Hunter); see also McDonald v. Santa Fe Trail Transp. Co., 427 U.S. 273, 282 n.10 (1976) (seemingly rejecting the but-for standard and then, within the same paragraph, requiring it); Mark S. Brodin, The Standard of Causation in the Mixed-Motive Title VII Action: A Social Policy Perspective, 82 Colum. L. Rev. 292, 301 n.40 (1982) (calling the passage in McDonald “cryptic”); Robert S. Whitman, Note, Clearing the Mixed-Motive Smokescreen: An Approach to Disparate Treatment Under Title VII, 87 Mich. L. Rev. 863, 870 (1989) (accusing the Court in McDonald of having “contradicted itself”). With even the Supreme Court unable to keep its terms straight for an entire opinion, stable rules are unavailable to guide lower courts. Nor are courts alone in equivocating. Compare Tribe, supra note 24, at 19-20 (using a “but/for” test), with id. at 31-32 (rejecting a “but/for” test).

The words “mixed motives” are often used pejoratively. See, e.g., Robert Philip, The Marthas: Or, The Varieties of Female Piety 169 (1841) (“His eye was not single, even when his hand was most active and liberal. Rachel was the first to discover his mixed motives, and not slow to arraign them.”).

For attempts to do so, see, for example, Anjum Gupta, Nexus Redux, 90 Ind. L.J. 465 (2015), which advocates for a more proimmigrant mixed motives test in asylum law; and Margaret E. Johnson, Comment, A Unified Approach to Causation in Disparate Treatment Cases: Using Sexual Harassment by Supervisors as the Causal Nexus for the Discriminatory Motivating Factor in Mixed Motives Cases, 1993 Wis. L. Rev. 231, which advocates for a harmonized approach to sexual harassment disparate treatment claims.

See, e.g., Kaitlin Picco, The Mixed-Motive Mess: Defining and Applying a Mixed-Motive Framework, 26 A.B.A. J. Lab. & Emp. L. 461 (2011) (discussing the points at which mixed motives questions may be addressed).

See, e.g., Fallon, supra note 7, at 554-58 (considering the consequences of a finding of forbidden intent in the context of legislation).

On other limitations woven into this Article’s approach, see infra notes 66-80 and accompanying text.

See supra note 24.

For example, whether an asset is a security subject to federal regulation sometimes turns on investment motive. See SEC v. W.J. Howey Co., 328 U.S. 293, 301 (1946). Some purchases, such as of real property, frequently entail both a consumption and investment motive. William J. Carney & Barbara G. Fraser, Defining a “Security”: Georgia’s Struggle with the “Risk Capital” Test, 30 Emory L.J. 73, 109-10 (1981). Courts typically avoid mixed motives analysis by reading one motive out of the facts of the case. Either the “investors were attracted solely by the prospect of acquiring a place to live, and not by financial returns on their investments,” United Hous. Found., Inc. v. Forman, 421 U.S. 837, 853 (1975) (emphasis added), or else they were “attracted solely by the prospects of a return on their investment,” Howey, 328 U.S. at 300 (emphasis added). It bears noting that both Howey and Forman involved real property: an orange grove and an apartment, respectively.

See infra Appendix B.

Khanna v. McMinn, No. CIV.A. 20545-NC, 2006 WL 1388744, at *43­–44 (Del. Ch. May 9, 2006) (disqualifying a mixed motives shareholder who was also a former officer engaged in personal litigation with the company).

Subin v. Goldsmith, 224 F.2d 753, 761 (2d Cir. 1955); Youngman v. Tahmoush, 457 A.2d 376, 382 (Del. Ch. 1983) (“Though the plaintiff may well have in part a selfish motive in bringing this action, which is not unusual, he will be permitted to continue to act on behalf of [the class].”).

11 U.S.C. § 1126(e) (2012).

See In re Landing Assoc., Ltd. 157 B.R. 791, 803 (Bankr. W.D. Tex. 1993) (“The standard is both inherently fact-intensive and difficult to apply . . . .”). Further examples abound. See, e.g., Ozburn-Hessey Logistics, LLC v. 721 Logistics, LLC, 40 F. Supp. 3d 437, 454 n.4 (E.D. Pa. 2014) (discussing civil conspiracy).

42 U.S.C. §§ 2000e–2(a)(1) to (2), (m) (2012). However, such plaintiffs win only limited remedies (e.g., attorney’s fees, injunction against further discriminatory practices). A tougher “but-for” standard remains predicate to full recovery (e.g., compensatory damages or reinstatement to the lost job), but the burden is on the employer to disprove the causal significance of discrimination. 42 U.S.C. § 2000e-5(g)(2)(B) (A court “shall not award damages or issue an order requiring any admission, reinstatement, hiring, promotion, or payment” if the employer “demonstrates that [it] would have taken the same action in the absence of the impermissible motivating factor.”). Whitman points out that “the ‘same decision’ test is identical to the ‘but for’ test, which asks whether the discrimination was the ‘but for’ cause of the adverse action. Any distinction between the two is semantic only.” Whitman, supra note 29, at 876 n.79; accord Givhan v. W. Line Consol. Sch. Dist., 439 U.S. 410, 417 (1979).

The foregoing standard applies to only the five core Title VII identities (race, sex, religion, national origin, and color). Military status likewise requires plaintiffs to show that discrimination was a motivating factor and then shifts the burden to defendants to show that the same action would have occurred regardless. See 38 U.S.C. § 4311(c)(1) (2012). Prior to the enactment of the Uniformed Services Employment and Reemployment Rights Act of 1994, courts imposed liability only if the employee was adversely affected “solely” because of her past, present, or future enlistment. Monroe v. Standard Oil Co., 452 U.S. 549, 559 (1981). However, it seems that employers successful in carrying their burden avoid all liability when discrimination is on the basis of military status. See Staub v. Proctor Hosp., 562 U.S. 411, 421 (2011) (“Thus, if the employer’s investigation results in an adverse action for reasons unrelated to the supervisor’s original biased action (by the terms of USERRA it is the employer’s burden to establish that), then the employer will not be liable.”); accord Erickson v. U.S. Postal Serv., 571 F.3d 1364, 1368 (Fed. Cir. 2009); Gummo v. Vill. of Depew, 75 F.3d 98, 106 (2d Cir. 1996). Thus, unlike Title VII discrimination, plaintiffs will not recover anything unless discrimination was a but-for cause of the adverse action. See Charles A. Sullivan, Tortifying Employment Discrimination, 92 B.U. L. Rev. 1431, 1436 n.21 (2012).

In closely related suits, plaintiffs bear the burden of proving but-for causation from the very start, with no burden shifting or partial remedies based on a “motivating factor.” Those related suits concern (a) retaliation for complaining about discrimination (even core Title VII bias), (b) discrimination on the basis of age or disability, or (c) discrimination in non-employment contexts (e.g., obtaining an apartment or other commercial relation). Uniformed Services Employment and Reemployment Rights Act, 38 U.S.C. § 4311 (2012); see, e.g., Gross v. FBL Fin. Servs., 557 U.S. 167, 180 (2009) (holding that the Age Discrimination Act of 1967 is subject to the but-for standard). The ADA Amendments Act of 2008 (ADAAA) amended the ADA to prohibit discrimination “on the basis of” disability rather than “because of” disability, suggesting some difference from the language of Title VII discrimination. This tough test also applies to the five core Title VII protected statuses in non-employment contexts. For example, under 42 U.S.C. § 1981, all persons are afforded the equal right “to make and enforce contracts,” regardless of race. However, mixed motives discrimination in violation of this statute is covered by the tough “but-for” standard rather than the easier “motivating factor” of the 1991 Act. See Wheat v. Chase Bank, No. 3:11-CV-309, 2014 WL 457588, at *12 (S.D. Ohio Feb. 3, 2014); see also Equal Pay Act (EPA), 29 U.S.C. § 206(d)(1) (2012) (using the same “on the basis of sex” phrasing as the ADAAA). There is some disagreement about whether the ADA permits mixed motives analysis or whether mixed motives cases are instead shoehorned into the framework set out in McDonnell Douglass Corp. v. Green, 411 U.S. 792 (1973). Compare Parker v. Columbia Pictures Indus., 204 F.3d 326, 336-37 (2d Cir. 2000) (employing a mixed motives analysis under the ADA), with Layman v. Alloway Stamping & Mach. Co., 98 Fed. App’x. 369, 375-76 (6th Cir. 2004) (noting disagreement among the circuits regarding mixed motives under the ADA and disagreeing with Parker). And it applies in all retaliation suits, where an employer takes adverse actions to punish or discourage employees from seeking redress for discrimination. E.g., Univ. of Tex. Sw. Med. Ctr. v. Nassar, 133 S. Ct. 2517, 2520 (2013) (applying the “traditional principles of but-for causation, not the lessened causation test”); see also 42 U.S.C. § 2000e–3(a) (2012) (barring retaliatory employment actions); Gross, 557 U.S. at 180 (holding that the Age Discrimination Act of 1967 is subject to the but-for standard).

See infra Section III.A.2.

See J.E.B. v. Alabama, 511 U.S. 127, 129 (1994) (holding that “gender, like race, is an unconstitutional proxy for juror competence and impartiality”); Batson v. Kentucky, 476 U.S. 79, 89 (1986) (“[T]he Equal Protection Clause forbids the prosecutor to challenge potential jurors solely on account of their race . . . .”).

See, e.g., State v. Ornelas, 330 P.3d 1085, 1092 (Idaho Ct. App. 2014) (“[M]ost states have adopted what is . . . referred to as the per se approach . . . .”); accord Owens v. State, 531 So. 2d 22, 23­-24 (Ala. Crim. App. 1987); State v. Lucas, 18 P.3d 160, 163 (Ariz. Ct. App. 2001); Robinson v. United States, 878 A.2d 1273, 1284 (D.C. 2005); Rector v. State, 444 S.E.2d 862, 865 (Ga. App. 1994); McCormick v. State, 803 N.E.2d 1108, 1112–13 (Ind. 2004); State v. Shuler, 545 S.E.2d 805, 811 (S.C. 2001); Payton v. Kearse, 495 S.E.2d. 205, 210 (S.C. 1998); State v. King, 572 N.W.2d 530, 535 (Wis. Ct. App. 1997).

See Ornelas, 330 P.3d at 1092 (“[S]ome states and most federal circuits have adopted a mixed motives analysis, and the Ninth Circuit has adopted its own approach.”); see also Gattis v. Snyder, 278 F.3d 222, 234-35 (3d Cir. 2002); Weaver v. Bowersox, 241 F.3d 1024, 1032 (8th Cir. 2001); King v. Moore, 196 F.3d 1327, 1335 (11th Cir. 1999); Wallace v. Morrison, 87 F.3d 1271, 1274-75 (11th Cir. 1996); United States v. Tokars, 95 F.3d 1520, 1533 (11th Cir. 1996); United States v. Darden, 70 F.3d 1507, 1531 (8th Cir. 1995); Jones v. Plaster, 57 F.3d 417, 421 (4th Cir. 1995); Howard v. Senkowski, 986 F.2d 24 (2d Cir. 1993).

Cook v. LaMarque, 593 F.3d 810, 814-15 (9th Cir. 2010) (applying a third approach, the “motivated in substantial part” standard); see infra notes 138-144 and accompanying text.

See Foster v. Chatman, 136 S. Ct. 1737, 1754 n.6 (2016); Snyder v. Louisiana, 552 U.S. 472, 485 (2008).

471 U.S. 222, 232 (1985). For extensive treatment of Hunter, see infra notes 126-137 and accompanying text.

See, e.g., Mt. Healthy City Sch. Dist. Bd. of Educ. v. Doyle, 429 U.S. 274, 285-86 (1977) (using causation to analyze a mixed motives First Amendment claim); Nardone v. United States, 308 U.S. 338, 341 (1939) (evidence); Murray v. Groose, 106 F.3d 812, 814 (8th Cir. 1997) (jury selection); NLRB v. Vemco, Inc., 989 F.2d 1468, 1478 (6th Cir. 1993) (labor law).

Some Justices required but-for causation. Price Waterhouse v. Hopkins, 490 U.S. 228, 262 (1989) (Kennedy, J., dissenting). Others note that something need not be “the” cause to be “a” cause, id. at 242-45 (majority opinion), but they imposed a but-for test in order to qualify for meaningful remedies. Id. at 242; id. at 260 (White, J., concurring); id. at 268 (O’Connor, J., concurring); id. at 262 (Kennedy, J., dissenting). Causation continues to influence developments in employment jurisprudence. See, e.g., Univ. of Tex. Sw. Med. Ctr. v. Nassar, 133 S. Ct. 2517 (2013).

See, e.g., Gudel, supra note 21.

See United States v. Generes, 405 U.S. 93, 105 (1972) (“The Regulations’ use of the word ‘proximate’ perhaps is not the most fortunate, for it naturally tempts one to think in tort terms. The temptation, however, is best rejected, and we reject it here.”). The regulation provided, “For purposes of subparagraph (2) of this paragraph, the character of the debt is to be determined by the relation which the loss resulting from the debt’s becoming worthless bears to the trade or business of the taxpayer. If that relation is a proximate one in the conduct of the trade or business in which the taxpayer is engaged at the time the debt becomes worthless, the debt comes within the exception provided by that subparagraph.” 26 C.F.R. § 1.166-5(b)(2) (2016).

See Generes, 405 U.S. at 103-05 (considering policy arguments why the tort concept of causation “has little place in tax law, where plural aspects are not usual, where an item either is or is not a deduction, or either is or is not a business bad debt, and where certainty is desirable”); see also Weddle v. Comm’r, 325 F.2d 849, 852 (2d Cir. 1963) (Lumbard, C.J., concurring) (“To import notions of proximate causation distilled from the great body of tort law into consideration of [Section] 166 is of little value, because factors such as time, space, and foreseeability, and the very basic notion of causation in fact which underlies the law of proximate causation are by their nature incapable of application to a problem which requires dissection of different motivations toward a similar objective.”).

But see James J. Brudney & Corey Ditslear, The Warp and Woof of Statutory Interpretation: Comparing Supreme Court Approaches in Tax Law and Workplace Law, 58 Duke L.J. 1231, 1283 n.182 (2009) (citing without discussion the Generes dissent, which did not discuss tort causation at all).

This is a shame, since tax has a particularly rich engagement with mixed motives. See, e.g., Marvin Chirelstein, Federal Income Taxation: A Law Student’s Guide to the Leading Cases and Concepts 120-22 (1977); Michael J. Graetz, Implementing a Progressive Consumption Tax, 92 Harv. L. Rev. 1575, 1585-86 (1979).

See Univ. of Tex. Sw. Med. Ctr. v. Nassar, 133 S. Ct. 2517, 2546 (2013) (Ginsburg, J., dissenting) (criticizing “but-for” tests as difficult for judges and juries); Price Waterhouse v. Hopkins, 490 U.S. 228, 247 n.12 (1989) (discussing concern for jury trials); id. at 292 (Kennedy, J., dissenting) (expressing concern for jury trials).

See, e.g., Covey, supra note 19 (discussing mixed motives in jury selection).

See, e.g., Weber, supra note 23 (comparing six areas: contractual relations, malicious prosecution, defamation, retaliatory eviction, and concurrent loss tort and contracts cases).

See Katz, supra note 4, at 498 (ruling out “necessary, but not sufficient” cases as “unlikely to occur in the context of decisionmaking, where the relevant acts (for example, consideration of sex and consideration of tardiness) occur simultaneously” (emphasis omitted)); Weber, supra note 23, at 499 (defining mixed motives cases as ones where “two causes, either of which would alone cause the harm, operate simultaneously,” thereby limiting the inquiry to what I will later call Quadrant III).

E.g., Nancy M. Modesitt, Causation in Whistleblowing Claims, 50 U. Rich. L. Rev. 1193, 1201-10 (2016) (listing eight motive standard types without establishing that they actually entail different results).

See Hartley v. Fine, 780 F.2d 1383, 1387 (8th Cir. 1985) (explaining that the terms “motivating factor” and “substantial factor” are “interchangeable”); cf. Katz, supra note 4, at 491 n.5 (listing almost thirty different statements of the mixed motives standard in Hopkins).

One way to test this would be to see whether there are courts that say something to the effect of, “Of course there was a contributing factor here, and that would establish liability in our neighboring state. But not here, because it wasn’t quite a motivating factor.”

An alternative way of stating this claim is that no single scalar or statistic can accomplish all three goals.

See, e.g., Sam Stonefield, Non-Determinative Discrimination, Mixed Motives, and the Inner Boundary of Discrimination Law, 35 Buff. L. Rev. 85, 114-20 (1986). Stonefield is able to depict the relative strength of two motives to one another, but his chart does not communicate the absolute strength of the motives either individually or as a set. Therefore, a move toward the “more racist” side of his chart is both compatible with increasing racist motivation and with decreasing racist motivation (so long as nonracist motives are dropping even faster). Likewise, any point on the scale is compatible with any absolute level of racist motive, so long as nonracist motive is proportional. Thus, a but-for test or motivating factor test can be satisfied at any point on his line. This is not a trivial error. It leads Stonefield to erroneously infer that “determinative” racism (which means “but-for”) is stronger racism than “substantial” racism (which, in his language, means racism exceeding a minimum quantum of strength). Yet there is nothing in his theory that guarantees this result. And failure to notice this bizarre result may be what causes Professor Stonefield to define “substantial” as excluding trivial quantities.

Professor Brodin makes a similar move:

At one end of the spectrum is a test, specifically rejected by Congress, that requires the plaintiff to establish that the unlawful factor was the sole factor behind the decision. At the other end is a causal theory that prohibits a decision that was based in part on an impermissible consideration even if a legitimate reason was also relied on. In between is a test that would invalidate personnel action that was based in substantial part on a discriminatory ground, and another that requires the plaintiff to prove that the impermissible consideration was a determinative factor, i.e., a factor that a made a difference in the ultimate result.

Brodin, supra note 29, at 293 (footnotes omitted).

The spectrum that makes “in part” a lesser point than “substantial part” is either a ranking of the absolute strength of the motive or its strength relative to another motive. In either case, there is no assurance that determinative (i.e., but-for) should be further out than substantial part. A motive may be determinative, even if it is absolutely tiny and tiny relative to other motives, if the other motive is not individually sufficient to motivate the result.

Professor Modesitt makes this same move and another. Modesitt, supra note 61, at 1202-11. She ranks “but-for” as tougher than her “substantial factor” test. But then she puts both as easier tests than a primary factor test. Id. at 1203-05. Yet a motive might be primary without being determinative if even the secondary motive was strong enough to drive the result independently. And a motive might be primary and yet insubstantial if numerous trivial motives together added up to motivate the act.

Professor Katz does not make this error, but tempts his reader to make it when he asserts that “it is hard to imagine that it would be significantly easier for plaintiffs to prove sufficiency than it would be for them to prove necessity.” Katz, supra note 4, at 510 n.85. He is right that the bad motive is never larger for necessity than sufficiency, making necessity easier on that axis. But necessity requires someone to confront the contribution of the other motive—sufficiency does not require any such analysis. Whether it is easier to prove necessity than sufficiency will depend on the plaintiff’s ability to rebut claims about pressing legitimate motives, and we have no general theory about the relative difficulty of those tasks.

Alexander M. Bickel, The Least Dangerous Branch: The Supreme Court at the Bar of Politics 208-21 (2d ed. 1986) (distinguishing motive, a psychological fact, from intent or purpose); Intent, Black’s Law Dictionary (10th ed. 2014) (“While motive is the inducement to do some act, intent is the mental resolution or determination to do it.”); Stephen, supra note 4, at 110-12. Purpose is sometimes the same as motive, sometimes the same as intent, and sometimes independent. Walter Wheeler Cook, Act, Intention and Motive in the Criminal Law, 26 Yale L.J. 645 (1917) (distinguishing between intent, motive, and purpose). The Model Penal Code distinguishes between various levels of culpability, from “negligently” to “recklessly” to “knowingly” to “purposely.” Model Penal Code §§ 2.02(2)(a)-(d) (Am. Law. Inst. 1962). This Article’s analysis would seem to be applicable only when an actor proceeds purposely.

See, e.g., Pullman-Standard v. Swint, 456 U.S. 273, 289-90 (1982) (conflating motive and intent); Mobile v. Bolden, 446 U.S. 55, 62-63 (1980) (conflating motive and purpose); Palmer v. Thompson 403 U.S. 217, 241 (1971) (White, J., dissenting) (conflating motive and purpose); Griggs v. Duke Power Co., 401 U.S. 424, 429 (1971) (conflating purpose and intent).

See, e.g., Wayne R. LaFave & Austin W. Scott, Jr., Handbook on Criminal Law § 3.6(a), at 229 (2d ed. 1986); John William Salmond, Jurisprudence, or, The Theory of the Law 347 (3d ed. 1910) (defining motive as “ulterior intent”). Still others reject any effort to categorize these various concepts. John Hart Ely, Legislative and Administrative Motivation in Constitutional Law, 79 Yale L.J. 1205, 1217-21 (1970); David A. Strauss, Discriminatory Intent and the Taming of Brown, 56 U. Chi. L. Rev. 935, 951 (1989) (noting the interchangeability of these words in equal protection law).

Thus, I assume it is sensible to say that a teacher was fired because the school board wanted to silence political dissent (motive), and that this is different from merely noting that the firing was not the result of a clerical error (intent). I do not attempt to answer the question of whether it is fruitful to characterize the action in terms of a highly specific intent (e.g., “the board intended to fire a political dissenter”) combined with a more generalized intent (“the board sought to have a ‘good’ set of teachers”), except to say that my usage of motive should still attach to this version of specific intent. For example, I take Professor Fallon’s recent article on legislative intent to nevertheless address material that this article analyzes as motive. Fallon, supra note 7. On multiple overlapping characterizations of an action, see Donald Davidson, Agency, in Essays on Actions and Events 43, 57-61 (2001) (discussing the multiple potential characterizations of any given action, many of which call attention to a different psychological aspect of the actor).

A closely related question is whether the agent must “endorse” her motives in some way, or whether unendorsed mental states may be relevant. See generally Angela M. Smith, Conflicting Attitudes, Moral Agency, and Conceptions of the Self, 32 Phil. Topics 331 (2004) (arguing against the endorsement requirement).

See Oliver Wendell Holmes, Jr., Privilege, Malice, and Intent, 8 Harv. L. Rev. 1, 1 (1894); see also Ronald A. Cass & Keith N. Hylton, Antitrust Intent, 74 S. Cal. L. Rev. 657, 659 (2001) (making a similar claim regarding intent in antitrust law).

See Gudel, supra note 21, at 74 (“Motives, in sum, are a class or species of reasons for action.”); accord Owen MFiss, A Theory of Fair Employment Laws, 38 U. Chi. L. Rev. 235, 297 (1971); cf. Byrne Hessick, supra note 24, at 95 (2006) (“[A] defendant’s motives are her reasons for acting.”); Walter Harrison Hitchler, Motive as an Essential Element of Crime, 35 Dick. L. Rev. 105, 105 (“Motive is a desire prompting conduct.”). And a reason is something that motivates rather than justifies action. On the distinction, see Jonathan Dancy, Practical Reality (2000). To the degree that something other than reasons are considered, such as problematic beliefs or circumstances, the framework in this Article may or may not be useful.

See supra text accompanying note 5. See generally Richard Peters, The Concept of Motivation 34-35 (1958) (distinguishing between conscious motives (i.e., “his reason”) and potentially subconscious motives (i.e., “the reason”)). A vast psychological literature studies the ways in which attitudes and factual perceptions can be subject to distortion or bias. It is therefore easy to imagine an employer firing an employee, thinking that the reason pertains only to merit, but where the boss was more attentive to the employee’s faults because of the boss’s unconscious reactions to the employee’s race. Such cases are not the focus of this Article.

See, e.g., Janice Nadler & Mary-Hunter McDonnell, Moral Character, Motive, and the Psychology of Blame, 97 Cornell L. Rev. 255, 267-71 (2012) (discussing the ways in which perceptions and conclusions may be influenced by “motivations” where motivations involve having a preferred outcome).

See, e.g., Price Waterhouse v. Hopkins, 490 U.S. 228, 250 (1989) (“In saying that gender played a motiving part in an employment decision, we mean that, if we asked the employer at the moment of the decision what its reasons were and if we received a truthful response, one of those reasons would be that the applicant or employee was a woman.”).

See Donald Davidson, Actions, Reasons, and Causes, 60 J. Phil. 685 (1963) (arguing that reasons cannot be causes).

See H.L.A. Hart & Tony Honoré, Causation in the Law (1959) (examining causation in law, but nevertheless rejecting determinism); see also, D. Don Welch, Removing Discriminatory Barriers: Basing Disparate Treatment Analysis on Motive Rather than Intent, 60 S. Cal. L. Rev. 733, 739 (“Motive is a causal concept.”). But see Richard W. Wright, The NESS Account of Natural Causation: A Response to Criticisms, in Perspectives on Causation 285 (Richard Goldberg ed., 2011) (embracing deterministic causation for human action).

See supra notes 50-56 and accompanying text.

See supra notes 66-69 and accompanying text.

It seems that it will often be appropriate to group and sum the various A-Motives and (separately) B-Motives. Then this model still allows comparison through its two-motive presentation. Yet one might wonder whether this is always appropriate. In a case with three equal motives, each might be a but-for motive, yet none is in itself primary. The choice of how to combine them is the choice of whether to find a Primary Motive at all. Such considerations require greater attention than can be accomplished at this time.

Klein, supra note 18, at 1108-09.

The impossibility of interpersonal comparison of utility has been a defining feature of modern economic thought. See, e.g., 3 Elie Halévy, La Formation du Radicalisme philosophique 481 n.55 (1904) (quoting Jeremy Bentham for the observation that “you might as well pretend to add 20 apples to 20 pears” (quoting Jeremy Bentham, Dimensions of Happiness (unpublished manuscript) (on file with University College London))).

Katz distinguishes between strong sufficiency and weak sufficiency. Katz, supra note 4, at 497 n.25. Strong sufficiency is satisfied if the factor in question would have led to the observed result irrespective of whether any other factors were subtracted. Weak sufficiency means that the factor would have only caused the result with the other factors present. Katz addresses only weak sufficiency in his article because he finds strong sufficiency to be a dubious concept. What could cause a result without any help at all—without oxygen, for instance?

In this Article, I invoke neither strong nor weak sufficiency. Instead, I favor an intermediate position: a motive is sufficient if it would have led to the observed result even if other contributing motives were subtracted. This is stronger than weak sufficiency because it asks what would have happened in the absence of other background motives, but it is weaker than strong sufficiency because it does not require that the motive would spur action even if other nonmotive facts were greatly altered. Within this notion of sufficiency, it should be clear that I am describing a sort of “independent sufficiency” even if I do not always use the word “independent.”

Katz refers to individually insufficient motives, which are neither necessary nor sufficient, as exhibiting “minimal causation.” Katz, supra note 4, at 499. I avoid that term in part because I wish to avoid endorsing without argument the controversial notion that motives must be “causal” to be relevant. See supra notes 76-78 and accompanying text. Nevertheless, the language of causation may prove useful to some readers, either because they subscribe to a causal theory of motivation or because they are familiar with its terminology. For such readers, I include the corresponding causal language as well. In such language, we might think of Adam’s A-Motive as a necessary and sufficient cause of Adam’s actions, while Betty’s A-Motive is neither necessary nor sufficient. In a counterfactual sense, removing Adam’s A-Motive (and only removing that motive) would change Adam’s action, while removing Betty’s A-Motive alone would in no way change the results.

Of course, even Adam’s A-Motive is not sufficient in the strongest sense, see supra note 83, since Adam would not act if, say, all oxygen in the universe disappeared.

Stephen, supra note 4, at 121 (“[A] man’s motives for any given act . . . are always mixed.”). But see Marcia W. Baron, Kantian Ethics Almost Without Apology 152-55 (1999) (questioning the prevalence of mixed motives); Judith Baker, Do One’s Motives Have To Be Pure?, in Philosophical Grounds of Rationality: Intentions, Categories, Ends 457, 457-58 (Richard E. Grandy & Richard Warner eds., 1986) (same).

See supra text accompanying note 30. Other times, A-Motives and B-Motives may both be bad. See Hunter v. Underwood, 471 U.S. 222, 231 (1985) (discussing how an unlawful motive—disenfranchising blacks—was used as political cover for a lawful but distasteful motive—disenfranchising poor whites). Note also that the relevant motive may not even be that of a party to the litigation. Alpha’s tax obligations may turn on Beta’s motive in giving a putative gift, even if Beta is not a party to the litigation—and even if Beta is no longer living. See, e.g., United States v. Harris, 942 F.2d 1125 (7th Cir. 1991); see also Gupta, supra note 31, at 479 (noting that asylum proceedings inquire into the motive of a persecuting government, though the parties to the litigation are only concerned with the rights of an individual asylum seeker against U.S. immigration officials).

See Treas. Reg. §§ 1.162-2(b)(1) to (2) (1960) (considering whether the trip is primarily related to trade or business or primarily personal); see also United States v. Gotcher, 401 F.2d 118 (5th Cir. 1968) (evaluating an example of such a business trip).

If applying the language of tort causation, we would say that A-Motive was neither a necessary nor a sufficient cause, while B-Motive was both necessary and sufficient. A cause is necessary if the effect would not have occurred in the absence of that cause. In parallel, B-Motive is necessary because Charley would not have acted if his B-Motive had been extinguished. It is common to refer to necessary causes as but-for causes.

See, e.g., Price Waterhouse v. Hopkins, 490 U.S. 228, 235 (1989)The employee was described as “unduly harsh, difficult to work with and impatient with staff.” Id. The head of Hopkins’s department told her to “walk more femininely, talk more femininely, dress more femininely, wear make-up, have her hair styled, and wear jewelry.” Id. Another advisor suggested that she take “a course at charm school.” Id.

In the language of tort causation, this is analogous to a case of multiple sufficient causation.

The thought process may not be strictly additive, but A and B may cumulate to reach the necessary threshold together. In any case, I will treat the process as additive for ease of exposition.

My term follows Baron’s treatment of Kant on mixed motives. See Baron, supra note 85, at 152-55. Some might refer to this zone as one of overdetermination, or of multiple necessary causes, but I dislike those labels here. Overdetermination might suggest that either motive would have sufficed independently to determine the action, which is not true. Multiple-causation invokes causation, which is controversial.

See J.L. Mackie, The Cement of the Universe: A Study of Causation 43-47, 164-65 (1974) (“[I]f it is in principle undecidable whether the chocolate would on this particular occasion have come out if the shilling had not been put in, it is equally undecidable whether the putting in of the shilling caused the appearance of the chocolate.”); Louis E. Loeb, Causal Theories and Causal Overdetermination, 71 J. Phil. 525, 526 (1974) (“Cases of causal overdetermination seem relatively different—two events, states of affairs, conditions, or objects seem to have an equal claim to having played some one causal role.”). Of course, no single cause is ever truly sufficient to assure an effect. There are always other causes and background factors. Here, I really mean that as far as motives go each motive was sufficient for the action.

In familiar causal terms, we could think of Charley’s as a case of necessary and sufficient causation. A-Motive could be subtracted without any change (so it is not necessary, and B-Motive is sufficient) and B-Motive also could not be subtracted lest the action be aborted (so it is necessary, as well).

Or, rather, any action Eddy takes is not the result of motives A or B. If he acts, it is for some other motive, or else it is motiveless action, such as a reflexive spasm.

To summarize this in familiar causal metaphors, overdetermination refers to two sufficient but not necessary motives; sole determination refers to one necessary and sufficient motive paired with one minimally causal motive; hybrid cases consist of two necessary but not sufficient motives.

Notice also that this zone of predomination says nothing about when motives are precisely equal, though the law might nevertheless treat tied cases differently from those in which one motive exceeds the other by a small amount.

For any given motive, we can ask: Is the motive greater than q? Is it greater than 1? Is it the largest motive? Does the sum of all motives exceed 1?

See infra Appendix A. These are motive “standards” insofar as they specify the quanta of motives necessary for a party to prevail, just as standards of proof set the quanta of certainty about certain elements necessary for a party to prevail. See Standard of Proof, Black’s Law Dictionary (10th ed. 2014) (“The degree or level of proof demanded in a specific case, such as ‘beyond a reasonable doubt’ or ‘by a preponderance of the evidence’; a rule about the quality of the evidence that a party must bring forward to prevail.”). Just as the standard of proof leaves many questions unanswered, such as who must bear the burden of meeting that standard, a given motive standard likewise requires supplementation. The content of a full motive rule or approach would allocate the burden of proof, set the level of motive required for satisfaction, address any rules of evidence or burden shifting, and perhaps also address remedies. This Article focuses only on motive standards.

Miller v. Johnson, 515 U.S. 900, 916 (1995); accord Bush v. Vera, 517 U.S. 952, 959 (1996). Racially motivated gerrymanders are subject to strict scrutiny, which is often regarded as “‘strict’ in theory and fatal in fact.” Gerald Gunther, The Supreme Court, 1971 Term—Foreword: In Search of Evolving Doctrine on a Changing Court: A Model for a Newer Equal Protection, 86 Harv. L. Rev. 1, 8 (1972); cf. Adam Winkler, Fatal in Theory and Strict in Fact: An Empirical Analysis of Strict Scrutiny in the Federal Courts, 59 Vand. L. Rev. 793 (2006) (examining the results of strict scrutiny challenges).

Vera, 517 U.S. at 959; Miller, 515 U.S. at 916.

Note that no one is liable, on this chart, when total motivation is less than one. In that realm, no motivated action takes place. Therefore, either there is no act to discuss, or it was unmotivated (e.g., a muscle spasm). See infra Appendix A.

Restatement (Second) of Torts § 668 & cmt. c (Am. Law Inst. 1977).

Directors’ decisions are immunized from shareholder challenge if their motives were primarily loyal even if they had some personal interest in the decision. See generally Alan R. Palmiter, Reshaping the Corporate Fiduciary Model: A Director’s Duty of Independence, 67 Tex. L. Rev. 1351, 1389 n.151 (1989) (citing sources that discuss mixed motives in corporate law). Professor Jill Fisch states that courts defer to boards if they “can attribute management’s action to ‘any rational business purpose.’” Jill E. Fisch, Frankenstein’s Monster Hits the Campaign Trail: An Approach to Regulation of Corporate Political Expenditures, 32 Wm. & Mary L. Rev. 587, 624-25 n.212 (1991). While this sounds like a sole purpose test, the cases Professor Fisch cites as support for this claim actually utilize a primary purpose test. See Panter v. Marshall Field & Co., 646 F.2d 271, 304 (7th Cir. 1981); Johnson v. Trueblood, 629 F.2d 287, 293 (3d Cir. 1980); see also Cheff v. Mathes, 199 A.2d 548, 554 (Del. 1964). The reason that confusion is possible is that courts frequently say that the plaintiff prevails if the directors’ improper motive was primary or was the sole motive. E.g. Treco, Inc. v. Land of Lincoln Sav. & Loan, 749 F.2d 374, 377 (7th Cir. 1984) (“Delaware’s rule insulates a director’s action unless plaintiff shows that an impermissible motive, such as perpetuation of director control, was the ‘sole or primary purpose’ for the action.”) (quoting Panter, 646 F.2d at 297). Yet, the “Primary Motive” test is strictly easier for plaintiffs to satisfy than the “Sole Motive” test; any director who passes the Primary Motive test has a legitimate motive that is more pressing that the illegitimate one. Having two motives, the director necessarily survives the Sole Motive test. Thus, despite references to Sole Motive, and despite the fact that courts often do find just one motive, see, e.g., Strassburger v. Earley, 752 A.2d 557, 575 (Del. Ch. 2000) (finding that the business judgment rule was rebutted because “a repurchase of Hesperus’s shares could further only one purpose—to confer absolute control”), the best statement of the test is as a Primary Motive test.

Klein, supra note 18, at 1104; accord Blum, supra note 14, at 508.

See Olk v. United States, 536 F.2d 876, 879 (9th Cir. 1976) (accepting dominant motive as the relevant legal standard). The Court in Commissioner v. Duberstein uses both the “dominant reason” language, and “detached and disinterested generosity.” 363 U.S. 278, 285-86­­ (1960). The latter might seem to imply a more restricted standard, such as a motivating factor test. However, subsequent decisions have clearly accepted that a payment is a “gift” if the dominant reason for it is detached and disinterested, and that this is compatible with secondary reasons that are interested. See, e.g., Lane v. United States, 286 F.3d 723, 729 (4th Cir. 2002); Poyner v. Comm’r, 301 F.2d 287, 291 (4th Cir. 1962); Froehlinger v. United States, 217 F. Supp. 13, 17 (D. Md. 1963), aff’d, 331 F.2d 849 (4th Cir. 1964). Thus, the mixed motives standard here is Primary Motive.

Bank of Palm Beach & Tr. Co. v. United States, 476 F.2d 1343, 1350 (Ct. Cl. 1973) (“While this case, as in all the death benefit cases we have researched, contains a multiplicity of motives—some favoring gift treatment, others favoring business treatment—we conclude that the . . . dominant motive in continuing the salary and bonus payments . . . was proximately related to business.”).

United States v. Generes, 405 U.S. 93, 104 (1972). Slight permutations on the facts of Generes iterate endlessly, essentially always subject to a predominant, primary, or dominant motive test. See Proximate Connection of Debt with Taxpayer’s Trade or Business, [Income] U.S. Tax Rep. (RIA) ¶ 1665.301 (2016) (collecting cases).

Section 162 allows a taxpayer to deduct “all the ordinary and necessary expenses paid . . . in carrying on any trade or business.” I.R.C. § 162(a) (2012). Courts use a predominant purpose test to determine whether deduction is available for an expense with plausibly both personal and business motivations. See, e.g., Mohn v. United States, No. 99-CV-76369, 00-CV-74575, 2001 WL 1399366, at *5 (E.D. Mich. Sept. 6, 2001) (finding that a question of fact exists in regards to which motive predominates for repayments following a failed investment scheme); Jenkins v. Comm’r, 47 T.C.M. (CCH) 238 (T.C. 1983) (permitting deduction for repayments of discharged indebtedness made “with the Primary Motive of protecting his personal business reputation [as a singer/songwriter]”); cf. McCann v. United States, 696 F.2d 1386, 1388 (1983) (using the Primary Purpose test to distinguish business travel from pleasure travel).

Mt. Healthy City Sch. Dist. Bd. of Educ. v. Doyle, 429 U.S. 274 (1976).

See, e.g., Hartman v. Moore, 547 U.S. 250, 260 (2006); Bd. of Educ., Island Trees Union Free Sch. Dist. No. 26 v. Pico, 457 U.S. 853, 871 n.22 (1982) (“By ‘decisive factor’ we mean a ‘substantial factor’ in the absence of which the opposite decision would have been reached”); Givhan v. W. Line Consol. Sch. Dist., 439 U.S. 410, 417 (1979) (remanding to determine whether exercise of First Amendment rights was a but-for cause, rather than “the primary” reason); Doyle, 429 U.S. at 274.

The defendant is liable in Quadrant I because here the B-Motive is itself sufficient to motivate action, and the A-Motive is not. There would have been a different (or no) action without the B-Motive. Likewise, the hybrid cases in Quadrant IV are cases where neither the A- nor B-Motives were independently sufficient for action, but the presence of B was enough (when supplemented by A-Motive) to just barely motivate the action. Again, because B seems to result in an altered state of affairs, it may be considered a but-for cause of the action. By contrast, Quadrant III shows too little B-Motive to independently motivate action, and the A-Motive is strong enough to be effective without bolstering. And Quadrant II likewise shows an A-Motive strong enough that conduct would have been motivated without B, even though the B-Motive was very strong and could have motivated the action independent of any A-Motive.

The But-For Motive standard is triggered if (B > 1 or B + A > 1) and A < 1. Since we only observe motivated acts when B or B + A exceeds 1, the plaintiff prevails under the But-For Motive standard any time except when A > 1.

See supra note 42.

SEC v. Masri, 523 F. Supp. 2d 361, 372 (S.D.N.Y. 2007).

Air Line Pilots Ass’n, Int’l v. E. Air Lines, Inc., 863 F.2d 891, 911-12 (D.C. Cir. 1988), cert. dismissed, 501 U.S. 1283 (1991), and cert. dismissed, 508 U.S. 948 (1993). See generally Cynthia L. Estlund, Economic Rationality and Union Avoidance: Misunderstanding the National Labor Relations Act, 71 Tex. L. Rev. 921, 942 (1993) (describing the National Labor Relations Board’s analysis of “mixed motive” cases).

U.S. Const. art I, § 9, cl. 3 (barring ex post facto federal laws).

Wiley v. Bowen, 824 F.2d 1120, 1122 (D.C. Cir. 1987); accord Flemming v. Nestor, 363 U.S. 603, 612-21 (1960); Jane Harris Aiken, Ex Post Facto in the Civil Context: Unbridled Punishment, 81 Ky. L.J. 323, 353-59 (1993).

Dan B. Dobbs, Paul T. Hayden & Ellen M. Bublick, The Law of Torts § 625 (2d ed. 2011). Dobbs notes that mixed motives are ubiquitous, so liability is unlikely in these cases. Id. (citing Havana Cent. NY2 LLC v. Lunney’s Pub, Inc., 49 A.D.3d 70, 74 (N.Y. App. Div. 2007) (noting that a defendant did not have the required sole motive to harm the plaintiff because there was “ample, unrefuted evidence” that the contested action was partially motivated by a desire to gain profits)).

See United States v. Avery, 137 F.3d 343, 358 (6th Cir. 1997); William M. Carter, Jr., Whren’s Flawed Assumptions Regarding Race, History, and Unconscious Bias, 66 Case Western Res. L. Rev. 947, 953 (2016). A similar test is applied for probable cause of searches generally. See Commonwealth v. Adams, 605 A.2d 311, 313 (Pa. 1992).

Holbrook v. Morrison, 100 N.E. 1111, 1111 (Mass. 1913) (discussing selling property to putatively undesirable owners); Rideout v. Knox, 19 N.E. 390, 391 (Mass. 1889) (discussing spite walls); cf. United States v. 480.00 Acres of Land, 557 F.3d 1297, 1308-11 (11th Cir. 2009) (noting that takings are judged by the “primary purpose” standard); Ronald J. Krotoszynski, Jr., Expropriatory Intent: Defining the Proper Boundaries of Substantive Due Process and the Takings Clause, 80 N.C. L. Rev. 713 (2002) (proposing that regulatory takings be judged by a primary purpose standard under the Due Process Clause). But see Obolensky v. Trombley, 115 A.3d 1016, 1023-25 (Vt. 2015) (using a primary motive test and citing five other states that adopt a primary motive test and nine states that adopt a sole motive test).

See, e.g., Goldstein v. Comm’r, 364 F.2d 734, 741 (2d Cir. 1966) (“[T]he deduction is proper if there is some substance to the loan arrangement beyond the taxpayer’s desire to secure the deduction.”). One arguable exception is Stratmore v. United States, where a taxpayer failed to carry his burden despite a stipulation that he indeed had two motives. 420 F.2d 461, 464 (3d Cir. 1970). In that case, the record contained no information to substantiate the relative importance of the motives—such as his salary relevant to the business motive or the amount at risk for the investment motive. Moreover, neither the government nor the court was clear about whether “significant factor” was even the appropriate test, rather than the tougher “primary” motive test. No court has followed Stratmore on this point.

Social Security Act § 1128B(b)(2), 42 U.S.C. § 1320a-7b(b)(2)(A) (2012) (criminalizing payment “to induce” purchase of items or services for which Medicare or Medicaid will ultimately make payment); see United States v. Narco Freedom, Inc., 95 F. Supp. 3d 747 (S.D.N.Y. 2015) (discussing the statute).

Narco Freedom, 95 F. Supp. 3d at 759; see also United States v. Borrasi, 639 F.3d 774, 782 (7th Cir. 2011) (compiling cases and adopting the any factor test).

This is the test that I will later argue covers the plaintiff’s initial burden in core Title VII employment discrimination cases. See infra Section III.A.2.

U.S. Const. amend. XIV, § 1.

Hunter v. Underwood, 471 U.S. 222 (1985).

Id. at 232.

Id. at 225 (quoting Underwood v. Hunter, 730 F.2d 614, 617 (11th Cir. 1984)) (citing Vill. of Arlington Heights v. Metro. Hous. Dev. Corp., 429 U.S. 252, 270 & n.21 (1977) and Mt. Healthy City Sch. Dist. Bd. of Educ. v. Doyle, 429 U.S. 274, 287 (1977)).

Id. at 232.

Id.

Its analysis would also clash with the application of the But-For standard in Arlington Heights and Mt. Healthy, the cases cited approvingly as the source of the standard. Moreover, it would clash with the analogous meaning of but-for causation in tort (which denies that X is a but-for cause, if Y would have led to the same result even if X were subtracted).

See infra Section III.C.

Underwood, 730 F.2d at 617 (“By allowing the state to prevail on what the district court concluded was a showing of permissible intent, the court brought its inquiry to a premature end.”).

See, e.g., Givhan v. W. Line Consol. Sch. Dist., 439 U.S. 410, 416-17 (1979) (remanding to determine whether the exercise of First Amendment rights was a but-for cause of termination, even though the trial court had determined that this was “the primary” reason for termination, and even though the Court of Appeals had held that the defendant had failed to make a successful “same decision anyway” defense).

It is also possible that the problems I identify were rhetorical choices, carefully chosen to nudge the Court regardless of the motive standard. In that case, terminological clarification would not have changed counsel’s word choice.

Brief for Appellants at 19, Hunter v. Underwood, 471 U.S. 222 (1985) (No. 84-76). This statement could also be read as a Sole Motive standard.

Id. at 20-21; see also id. at 32 (arguing that the court below “did not consider the possibility of the existence of an intention equal to the one they found to be impermissible”).

Cook v. LaMarque, 593 F.3d 810, 815 (9th Cir. 2010).

State v. Ornelas, 330 P.3d 1085, 1092 (Idaho Ct. App. 2014) (“[M]ost states have adopted what is . . . referred to as the per se approach, some states and most federal circuits have adopted a mixed-motives analysis, and the Ninth Circuit has adopted its own approach.”).

See infra Figure 12 (depicting this “Material Motive” test).

E.g., Crittenden v. Calderon, Nos. CIV S–95–1957 KJM GGH P, CIV S–97–0602 KJM GGH P, 2011 WL 2619097, at *26 (E.D. Cal. June 30, 2011).

See infra Section III.C.

Cook, 593 F.3d at 821 (emphasis added).

Id. at 826 (emphasis added).

Cf. Price Waterhouse v. Hopkins, 490 U.S. 228, 262 (1989) (O’Connor, J., concurring) (rejecting the “mere discriminatory thoughts” standard). For more support of this view, see id. at 250 (majority opinion) (“In saying that gender played a motivating part in an employment decision, we mean that, if we asked the employer at the moment of the decision what its reasons were and if we received a truthful response, one of those reasons would be that the applicant or employee was a woman.”). See generally Catherine T. Struve, Shifting Burdens: Discrimination Law Through the Lens of Jury Instructions, 51 B.C. L. Rev. 279, 298-302 (2010) (reviewing Justices’ memoranda and notes to show Justice Brennan’s desire to accommodate Justice O’Connor’s concerns while avoiding a connotation that “the discrimination must be of a certain magnitude before the burden must shift”).

Maestas v. Segura, 416 F.3d 1182, 1188 (10th Cir. 2005).

See Rebeca Hanner White & Linda Hamilton Krieger, Whose Motive Matters?: Discrimination in Multi-Actor Employment Decision Making, 61 La. L. Rev. 495, 505 n.66 (2001) (“Left to be determined . . . is what is meant by ‘a motivating factor.’”). The “motivating factor” formulation adopted in the statute was only one of over twenty different formulations offered up by the plurality and concurring opinions in Price Waterhouse. See Katz, supra note 4, at 491-92 n.5 (listing the various formulations).

Carey v. Mt. Desert Island Hosp., 156 F.3d 31, 39 (1st Cir. 1998) (reviewing a judge’s reply to a jury’s request of a definition for “a motivating factor” and noting “the controversy that exists” over the definition); Defendant’s Reply to Plaintiffs’ Objections to Defendant’s Jury Instructions, Brown v. Bank of Am. Corp., No. 107CV00105, 2008 WL 7254694, at *4 (D. Me. Aug. 22, 2008) (arguing that “the proposed jury verdict form they have submitted is legally incorrect in that it . . . states that the Plaintiffs only have to show that discrimination was ‘a factor’ when the mixed motive law clearly requires that they establish that it was a ‘motivating factor’”).

See, e.g., Michael Wells, Three Arguments Against Mt. Healthy: Tort Theory, Constitutional Torts, and Freedom of Speech, 51 Mercer L. Rev. 583, 588-89 (2000); Heather K. Gerken, Note, Understanding Mixed Motives Claims Under the Civil Rights Act of 1991: An Analysis of Intentional Discrimination Claims Based on Sex-Stereotyped Interview Questions, 91 Mich. L. Rev. 1824 (1993).

Gudel, supra note 21, at 70.

See infra Figure 12 and accompanying text.

See infra Figure 13 and accompanying text.

See infra Figure 14 and accompanying text.

See supra Figure 5 and accompanying text.

At times, Mark Weber advocates for something like a Sufficient Motive standard. Cf. Weber, supra note 23, at 499 (defining mixed motives cases as those where “two causes, either of which would alone cause the harm, operate simultaneously”); id. at 495 (advocating plaintiff victory in all mixed motives cases).

See Restatement (Third) of Torts: Liab. for Physical and Emotional Harm §§ 26, 27 (Am. Law Inst. 2010); see also infra note 158 (discussing causation in tort law).

See Katz, supra note 4, at 494 (advocating for what amounts to a Causal Motive test).

Restatement (Third) of Torts, supra note 156, at § 26. Language in the First and Second Restatements might have allowed exclusion of tiny but-for causes from causal characterization. See Restatement (Second) of Torts: What Constitutes Legal Cause § 431 cmt. a (Am. Law. Inst. 1965) (“[I]t is not enough that the harm would not have occurred had the actor not been negligent . . . . The negligence must also be a substantial factor in bringing about the plaintiff’s harm.”). That formulation was criticized for muddling the factual question of causation (causation-in-fact) from the evaluative question of responsibility (proximate causation). Restatement (Third) clarifies that small but-for causes are causes-in-fact. Restatement (Third) of Torts, supra note 156, at § 26 cmt. j (eliminating discretion for the fact finder to find no factual causation on grounds that putative cause was not sufficiently substantial); id. at § 27 cmt. b (eliminating discretion in the same manner for multiple causes). To the degree that small causes deserve special treatment, it is at another state of adjudication that is concerned with responsibility. While the Restatement preserves the possibility that an actor should be exempt from liability where their contribution was “only a trivial contribution,” that exemption does not arise by way of a causation analysis. Id. at § 36 cmt. b (“The limitation on the scope of liability provided in this Section is not applicable if the trivial contributing cause is necessary for the outcome . . . .”). The actor (and his conduct) remain a cause. The exemption is effected by way of a scope of liability analysis. Id.

Restatement (third) of Torts, supra note 156, at § 36 cmt. b (“[T]he actor who negligently provides the straw that breaks the camel’s back is subject to liability for the broken back.”).

The Sufficient Factor test goes even further afield, finding for the defendant in the entire IV quadrant.

See, e.g., Katz, supra note 4, at 503.

See, e.g., id. at 492 n.10. It also clashes with the legislative history. The 1991 Amendment was intended to make life easier for plaintiffs, which is certainly how the law has been understood by subsequent treatment. Plaintiffs’ lawyers have lamented the shrinking coverage of Price Waterhouse and the 1991 Amendment. Yet a plaintiff with good evidence that the defendant’s motive was within IVAb would do better if forced to carry the whole burden of proving but-for causation of the same result, rather than accept the supposedly solicitous motivating factor test.

Both stand on secure footing with respect to tort principles. The two rules differ only as to Quadrant III, a region where the Restatement is agnostic. Restatement (Third) of Torts, supra note 156, at § 27 cmt. f (“Sometimes, one actor’s contribution may be sufficient to bring about the harm while another actor’s contribution is only sufficient when combined with some portion of the first actor’s contribution. Whether the second actor’s contribution can be so combined into a sufficient causal set is a matter on which this Restatement takes no position and leaves to future development in the courts.”); cf. id. at cmt. i (noting “[t]he difficulty with dismissing” the “de minimis causal candidates and others that are overwhelmed by an independently sufficient cause . . . as not causally connected to the plaintiff’s harm”). Influential tort scholars have advocated for liability in that context. E.g., Richard W. Wright, Causation in Tort Law, 73 Calif. L. Rev. 1735, 1794 (1985); see also Weber, supra note 23, at 517 (“The vast majority of legal sources rely on philosophers’ arguments to conclude that any causal factor that contributes to a harmful decision is a cause-in-fact of the full harm.”). Recall that in Quadrant III, A-Motive is sufficient on its own to motivate action and B-Motive is neither independently sufficient nor is it necessary, given the strength of the A-Motive. It is not tempting to regard the B-Motive as a cause; it is like the match that is tossed onto a blazing inferno. And yet, the Restatement approach does not rule it out.

The argument is that small causes, though dwarfed by a larger cause, do still have a causal impact. They assure the outcome against some set of background facts, namely a partial slice of the presently robust alternative cause. They are therefore necessary elements of a sufficient set, which according to scholars such as Richard Wright, is what we mean by “cause.” The tiny match is a necessary member of a causally sufficient set: the portion of the inferno that was not quite big enough to destroy the house is made big enough by the match. Likewise, the portion of the A-Motive that was not sufficient to motivate the action can be thought to sum with the B-Motive. Finding causation in Quadrant III in the analogous mixed motives case would lead to an Any Motive test.

Whether this is a sound conclusion, whether fires and motives can be sub-divided, is plainly controversial, which is why the Restatement noted the possibility and neither endorsed nor rejected it.

See, e.g., Kell v. AutoZone, Inc., No. 07AS04375, 2014 WL 509143, at *12 (Cal. Ct. App. Feb. 10, 2014, as modified Feb. 24, 2014) (affirming a verdict in favor of the plaintiff based on the harmless error of the jury instruction requiring a “motivating factor,” rather than the “heightened standard of causation, requiring the plaintiff . . . to prove that the illegal criterion was ‘a substantial motivating factor’”).

Cf. Weber, supra note 23, at 495 (advocating for full recovery in all mixed motives employment cases).

Nor are courts systematic in preserving the linguistic illusion that they are using something other than an Any Motive test. For example, in Singh v. Gonzales, the test requires that the defendant “was motivated, at least in part, by one of the protected characteristics.” 406 F.3d 191, 197 (3d Cir. 2005). The court then cites three other cases for support of this rule: one requires that the action was “motivated in significant part” and the other two use an Any Motive test. Id. at 198. The word “significant” loses any meaning in its precedential application.

Even more parsimony could be claimed. Sole Motive is itself a subset of But-For and Primary Motive. Any time a motive is solitary, it will also be a necessary motive and larger than any other motives.

Note that many areas of law use more than one test, due to circuit splits or differing rules from state to state.

See supra Section III.A.2.

For an example, consider the law on civilian unauthorized recordings. There, the defendant loses if her unlawful motive (e.g., blackmail) is either a But-For or Primary Motive. United States v. Dale, 991 F.2d 819, 841-42 (D.C. Cir. 1993). Thus, it would inculpate in Quadrants I, IIB, and IV.

This does not always seem to have impressed itself on even very able scholars. Bill Klein urges allowing tax deductions for putative business expenditures if the business aspect was a “sufficient” motive. Klein, supra note 18, at 1111. That is, he would give A-Treatment if A>1. That is identical to giving B-Treatment if B (non-business reasons, like vacations) was a but-for cause of the trip. Klein might have realized he was advocating for a but-for test, but one imagines he would have made that understanding more transparent, given that but-for tests are so thoroughly disliked by tax scholars—including Klein himself. See id. at 1112 (explaining the problems with a but-for test).

Professor Stephen Gottlieb identifies four ways that courts establish motives: rational basis (no other motive exists); strict scrutiny (no other sufficient motive exists, given alternatives); natural and probable consequence (the result was probably the goal); and confession. See Stephen E. Gottlieb, Commentary: Reformulating the Motive/Effects Debate in Constitutional Adjudication, 33 Wayne L. Rev. 97, 102-03 (1986). The first two are attempts to locate B-Motive and assess the legal result solely by probing the strength and plausibility of A-Motive.

For example, it may be that the best way to decide whether an A-Motive would have motivated an action is to look at the defendant’s overwhelming and protracted commitment to B-Motives. Perhaps this is based on an empirical theory of motivation correlation, such that individuals almost never have high A and B motivations. Thus, a But-For test may sometimes involve recourse to B- and not just A-Motives.

See 38 U.S.C. § 4311(c)(1) (2012).

Indeed, I argue as such in other work. See Andrew Verstein, The Failure of Mixed Motives (unpublished manuscript) (on file with author).

These challenges are not handled through full trials. See Cook v. LaMarque, 593 F.3d 810, 828 (9th Cir. 2010) (Hawkins, J., dissenting) (noting sparse record); accord Covey, supra note 19, at 323; Deborah C. Malamud, The Last Minuet: Disparate Treatment After Hicks, 93 Mich L. Rev. 2229, 2302-03 n.238 (1995). Many motives inquiries are likewise handled without a full hearing. See, e.g., City of Las Vegas v. Foley, 747 F.2d 1294, 1299 (9th Cir. 1984) (denying plaintiffs’ request to depose city officials as to their motives, even though their motives would control the constitutionality of a zoning decision).

Cf. Herman A. Moore Tr. v. Comm’r, 49 T.C. 430 (1968) (Tannenwald, J., concurring) (criticizing the Primary Motive standard in a tax case because of litigation expenses).

This project concerns liability for certain motivated acts. It is worth noting that the law could target non-acts or acts conducted without sufficient motivation. The former we call “thought crimes” and the latter we may call strict liability or, perhaps, negligence. Yet there is no need in a project about mixed motivation to inquire deeply into what sorts of persons deserve sanctions despite having intended nothing or done nothing.

Appendix B summarizes that information.

There are ten regions, each of which can be designated as proplaintiff or prodefendant. Thus, there are 2^10, or 1,024, combinations. Actually, the permutations are far greater once supporting rules are considered. For example, the burden of proof can shift from party to party, so that the same compound motive standard can be styled in several ways. For example, IVBa and II could place the burden on the plaintiff to show IVBa and II and then allow the defendant to rebut II to reduce damages.