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that the First Amendment bans restrictions on speech arising from hostility, sympathy, or self-interest. The fact is that courts cannot enforce this ban directly. If all this is so, the First Amendment rules of which I am speaking, though seemingly substantive in content, resemble in function such proceduralmechanisms as presumptions and shifting burdens of proof. Consider how a different body of law responds to the difficulty of proving motive. Under the labor laws, an employer may not discharge an employee because of union activity. A court deciding whether such an act has occurredwill shift the burden of proof on the question of motive to the employer once the employee has made a lesser (prima facie) showing.82 In so doing, the law in effect establishes a rebuttable presumption: the law presumes improper motive from a set of facts merely suggestive of it unless the employer proves its absence. The rules of First Amendment law work in a similar manner. They too operate, though not overtly, to make a rebuttable determination of improper motive on the basis of some set of facts-for example, a content-based classification-suggestive but not dispositive of it. It is in this sense that I have spoken of these rules as evidentiary in nature: they, no less than such procedural mechanisms as presumptions and shifting burdens, serve to ameliorate troublesome problems of proving motive by giving exceptional weight to certain evidentiary materials. This hypothesis suggests a reinterpretation of O'Brien. No longer should that decision be viewed as a broad-scale stricture against invalidating regulations of speech on the basis of improper motive. That understanding of the case has always conflicted with too much in the Court's rhetoric and decisions. O'Brien stands for a narrowerproposition,relating not to the proprietyof inquiring into motive, but to the means by which to conduct this inquiry. To be more precise, O'Brien stated not that motive was irrelevant, but only that it could not be proved by traditional methods. In so doing, the decision left open the option of adopting a different mechanism to discover motive. The Court, as the next Section of this Article shows, has chosen this course in its elaboration of First Amendment doctrine.
82
See NLRB v Transportation Management Corp, 462 US 393, 403 (1983). A similar though less potent proceduralmechanism,designed to accomplishthe same object,is used in Title VII cases. See Texas Department of Community Affairs v Burdine, 450 US 248,
252-53 (1981).