Paradox of Self-Amendment by Peter Suber beginning or approach to the historical understanding that must eventually answer the question fully, if we are to have a full answer. If the question is not thought empirical, then the claims of formal logic must be given unqualified recognition, which would completely bar the legal acceptability or validity of inconsistency. I believe that position has been sufficiently dealt with in Part One. Consistency is a virtue in both statutory and common law. In each, the existence of inconsistent rules is admitted, but the effects of applying inconsistent rules to the same case are mitigated or wholly blocked by devices such as canons of interpretation and construction, the doctrine of implied repeal and amendment pro tanto, equity jurisdiction, judicial attempts at reconciliation and powers of narrow reading, distinguishing, overruling, and nullification, and even "benign neglect" or disregard of one of the rules. All these devices reflect strong repugnance for applying inconsistent rules to the same party in the same sense at the same time. The basis for this repugnance is rarely articulated, but probably stems less often from a sense of theoretical inelegance or "impossibility" than from the gross unfairness and unconscionability of applied contradiction. My own belief is that inconsistencies in law are least likely to be accepted when they require incompatible acts from the same person or punish a mandatory or permissible act, and most likely to be accepted when they harmlessly infect the abstract concept of a useful procedure or institution such as self-amendment, some applications of the bootstrap doctrine (the jurisdiction of a court to determine its own jurisdiction), and the self- justification of constitutions and revolutions. Sometimes inconsistencies of the second type may be accepted only because they are overlooked. And of course in many such cases even logicians may disagree on whether a supposed contradiction in them is necessary or eliminable. But I suspect that even a consensus of logical opinion and a crusading legal advocate would fail to stir much reform spirit for the elimination of the second type of inconsistency. Our basic legal policy about contradiction seems to be: if it hurts or is unfair, eliminate it or prevent its application through adjudicatory devices; otherwise smile at the sweating logicians. The acceptability of at least some contradiction I take to have been established by Part One. Self-amendment is accepted despite the failure of the logical attempts to date to eliminate its contradiction. The mere fact that some contradiction or inconsistency is actually accepted has several important consequences. First, it falsifies the common view that no "actual" inconsistencies exist in law. According to this view, "apparent" inconsistencies abound, but (on the strong version of this view) in every pair of inconsistent rules, at least one member is void or (on a weaker version) a good judge will never apply inconsistent rules to the same party at the same time. Either the inconsistent rules include some nullities, or they succeed each other in time,[Note 19] or they are applicable only in spatially distinct jurisdictions, or they are reconcilable in application by various devices at the judge's disposal. This view is either false or beside the point. If it applies only to inconsistencies between substantive rules, then it does not reach cases like self- amendment and we cannot assume the unreality of all legal contradiction. If it purports to reach all inconsistencies, then it is falsified by the historical acceptance of inconsistencies such as self-amendment. Second, a well-known rule of standard, formal logic declares that all propositions (including all contradictions) follow from any contradiction. If some contradictions are legally acceptable, then logically all others would follow. But legally not all do follow. That not all contradictions are legally accepted I take to be an empirical proposition of even greater certainty than the acceptability of some contradiction. But if we suppose that some but not all contradictions are actually accepted, then the logical rules of inference that would require all if any contradiction are obviously inapplicable to law or not fully operative within it. Rules of deductive inference may have a role to play in law, but they are not permitted to validate as law every proposition that is strictly deducible from propositions already validated as law. Hence the often quoted statement of Lord Halsbury in Quinn v. Leathem, (1901) A.C. 495 at 506: [A] case is only authority for what it actually decides. I entirely deny that it can be quoted for a proposition that may seem to follow logically from it. Such a mode of reasoning assumes that the law is necessarily a logical code, whereas every lawyer must acknowledge that the law is not always logical at all. This means that arguments by reductio ad absurdum should have only limited force in law, for the "logical extreme" of an accepted proposition may not itself be an accepted proposition even though it follows infallibly by logical rules (hence, restates tautologously propositions that are already accepted). This actually undercuts a more basic argument form, the modus tollens, or the argument that a proposition is false if it implies a falsehood. In law, a rule may be legally valid and yet imply others that are legally invalid. The line separating the valid from the invalid, therefore, is not a logical line or is not formally ascertainable; it is always a question of policy. In law we do not "live with the consequences" of our acts and affirmations, at least not if this means the logical consequences. Every step is taken on policy grounds or in bad faith, for normative reasons or by fraudulent appeals to the inexorability of our premises and rules. The ways in which this does, and does not, abrogate the sense in which law is rule-like will be explored below in Sections 21.C and 21.D. It is true, however, that inconsistent substantive rules need not ever be "actualized" in the same case. But some of the devices for preventing the application of inconsistent rules do not eliminate the inconsistency itself; they merely prevent it from doing mischief in a single case. For example, the common law rules that a person should use her property so that it harms no one else, and that her rights in her property extend from the depths to the heavens, tug in opposite directions when a person contemplates building a tall, noisy, or malodorous building or business on her land. Her rights will be adjudicated without repealing either of the general principles. The inconsistency of the two principles in her case is probably settled for future parties similarly situated —at least until the attitudes toward business and community change again. In one sense this lessens the 157