  A familiar hypothesis of that kind involves the principle that disputes that are similar in morally relevant respects should be treated alike. This hypothesis dictates identifying morally relevant respects in cases, which introduces a role for further hypotheses involving more specific principles that pick out those respects. Consider an imaginary case, Roe v Doe, where Doe is ordered to compensate Roe for the damage that she incurred, which was caused by Doe’s action. In the currently relevant sense, a principle, e.g., that one is responsible for damage caused by one’s carelessness on some conception of due care, would be germane in case it identified the factor that was relevant to Doe’s liability. If it did, it would normatively explain why Doe was ordered to pay—it would show how it’s right that he was. At the same time, the principle would determine how this decision would bear on other cases, given the duty to treat like alike. It would reflect the facts that ground the duty of due care and the liability that due care entails that is articulated by the principle. A principle that figures in such a hypothesis must, first, justify resolving an actual or hypothetical contested case in a particular way; and, second, justify resolving past actual or hypothetical settled cases, i.e., cases the outcome of which is not in dispute in the instant case, in the way they were or would have been resolved. Hypotheses of this character have similar functions, whether they concern the action of institutions or of litigants. By picking out the morally relevant features of some aspect of institutional practice, hypotheses of principle function as explanations of the legal relevance of that aspect of the practice today.