LegalSpeak: Price Waterhouse v. Hopkins (1989)
But-for causation is a hypothetical construct. In determining whether a particular factor was a but-for cause of a given event, we begin by assuming that that factor was present at the time of the event, and then ask whether, even if that factor had been absent, the event nevertheless would have transpired in the same way. The present, active tense of the operative verbs of 703(a)(1) (“to fail or refuse”), in contrast, turns our attention to the actual moment of the event in question, the adverse employment decision. The critical inquiry, the one commanded by the words of 703(a)(1), is whether gender was a factor in the employment decision at the moment it was made. Moreover, since we know that the words “because of” do not mean “solely because of,” we also know that Title VII meant to condemn even those decisions based on a mixture of legitimate and illegitimate considerations. When, therefore, an employer considers both gender and legitimate factors at the time of making a decision, that decision was “because of” sex and the other, legitimate considerations—even if we may say later, in the context of litigation, that the decision would have been the same if gender had not been taken into account….
We have, in short, been here before. Each time, we have concluded that the plaintiff who shows that an impermissible motive played a motivating part in an adverse employment decision has thereby placed upon the defendant the burden to show that it would have made the same decision in the absence of the unlawful motive. Our decision today treads this well-worn path….
Finally, an employer may not meet its burden in such a case by merely showing that at the time of the decision it was motivated only in part by a legitimate reason. The very premise of a mixed-motives case is that a legitimate reason was present, and indeed, in this case, Price Waterhouse already has made this showing by convincing Judge Gesell that Hopkins’ interpersonal problems were a legitimate concern. The employer instead must show that its legitimate reason, standing alone, would have induced it to make the same decision.