'Dialogical Estoppel: As can be seen, the heart of the idea behind legal estoppel is the idea of consistency. A similar concept, “dialogical estoppel,” can be used to justify the libertarian conception of rights, because of the reciprocity inherent in the libertarian tenet that force is legitimate only in response to force. The basic insight behind this theory of rights is that a person cannot consistently object to being punished if he has himself initiated force. He is (dialogically) “estopped” from asserting the impropriety of the force used to punish him, because of his own coercive behavior. This theory also establishes the validity of the libertarian conception of rights as being strictly negative rights against aggression, the initiation of force. The point where punishment needs to be justified is when we attempt to inflict punishment upon a person who opposes the punishment. Thus, using a philosophical, generalized version of “dialogical” estoppel, I want to justify punishment in just this situation, by showing that an aggressor is estopped from objecting to his punishment. Under the principle of dialogical estoppel, or simply estoppel for short, a person is estopped from making certain claims during discourse if these claims are inconsistent and contradictory. To say that a person is estopped from making certain claims means that the claims cannot even possibly be right, because they are contradictory. It is to recognize that his assertion is simply wrong because it is contradictory. Applying estoppel in such a manner perfectly complements the very purpose of dialogue. Dialogue, discourse, or argument—terms which are used interchangeably herein—is by its nature an activity aimed at finding truth. Anyone engaged in argument is necessarily endeavoring to discern the truth about some particular subject; to the extent this is not the case, there is no dialogue occurring, but mere babbling or even physical fighting. Nor can this be denied. Anyone engaging in argument long enough to deny that truth is the goal of discourse contradicts himself, because he is himself asserting or challenging the truth of a given proposition. Thus, the assertion as true of anything that simply cannot be true is incompatible with the very purpose of discourse. Anything that cannot be true is contrary to the truth-finding purpose of discourse, and thus is not permissible within the bounds of the discourse. And contradictions are certainly the archetype of propositions that cannot be true. A and not-A cannot both be true at the same time and in the same respect. This is why participants in discourse must be consistent. If an arguer need not be consistent, truth-finding cannot occur. And just as the traditional legal theory of estoppel mandates a sort of consistency in a legal context, the more general use of estoppel can be used to require consistency in discourse. The theory of estoppel that I propose is nothing more than a convenient way to apply the requirement of consistency to arguers, to those engaged in discourse, dialogue, debate, discussion, or argument. Because discourse is a truth-finding activity, any such contradictory claims should be disregarded, they should not be heard, since they cannot possibly be true. Dialogical estoppel is thus a rule of discourse that rules out of bounds any inconsistent, mutually contradictory claims, because they are contrary to the very goal of discourse. This rule is based solely on the recognition that discourse is a truth-seeking activity and that contradictions, which are necessarily untrue, are incompatible with discourse and thus should not be allowed. The validity of this rule is undeniable, because it is necessarily presupposed by any participant in discourse.'

'The primary social evil of our time is lack of respect for self-ownership rights. Self-ownership is rendered meaningless if the right to own private property is not also respected. The unique relationship between a person and "his" body — his direct and immediate control over the body, and the fact that, at least in some sense, a body is a given person and vice versa ... is what constitutes the objective link sufficient to give that person better title to his body than any third party claimant, even his parents... Any outsider who claims another's body cannot deny this objective link and its special status, since the outsider also necessarily presupposes this in his own case. This is so because in seeking dominion over the other, in asserting ownership over the other's body, he has to presuppose his own ownership of his body, which demonstrates he does place a certain significance on this link, at the same time that he disregards the significance of the other's link to his own body.'

'To say a person is estopped from making certain claims means that ... he will not be heard to make a statement which is flatly inconsistent with his earlier behaviour (and which another relied upon). Principled application of the estoppel principle would result in a free society. For all coercive crimes could be: punished (if not by the state, then at least by victims or their agents or defenders); and all non-coercive "crimes" could not be enforced. Since an arguer is estopped from denying the validity of estoppel in general, he must accept its validity—and he must also accept the validity of the results of its application. [This] framework establishes the validity of the libertarian nonaggression principle, which has been shown by many others to justify a libertarian or at least a minimalist or night-watchman state. Thus, everyone "must" accept the validity of the free society; to urge otherwise is to argue for inconsistency, and to be inconsistent, and to necessarily be wrong.'

'Libertarians are consistently opposed to aggression, defined in terms of invasion of property borders, where property rights are understood to be assigned on the basis of self-ownership in the case of bodies. And in the case of other things, rights are understood on the basis of prior possession or homesteading and contractual transfer of title. For the foregoing reasons, libertarianism may be said to be the political philosophy that consistently favors social rules aimed at promoting peace, prosperity, and cooperation. And as I have argued elsewhere, because the state necessarily commits aggression, the consistent libertarian, in opposing aggression, is also an anarchist.' -- Elsewhere: -- '...anyone who is not an anarchist must maintain either: (a) aggression is justified; or (b) states do not necessarily employ aggression.' -- What It Means To Be an Anarcho-Capitalist by N. Stephan Kinsella

'"Argumentation ethics" is a defense of libertarian rights. Hoppe asserts that argumentation, or discourse, is by its nature a conflict-free way of interacting and requires individual control of resources [the body]; thus, he argues, certain norms are presupposed as true by anyone engaging in genuine discourse. These norms include the libertarian principle of non-aggression, which itself implies libertarian rights. Therefore, no one can argumentatively deny libertarian rights without self-contradiction. Kinsella's "estoppel" theory draws on Hoppe. Kinsella argues that an aggressor cannot coherently object to being punished for the act of aggression, by the victim or the victim's agents or heirs, i.e. he is "estopped" from withholding consent, because by committing aggression he commits himself to the proposition that the use of force is legitimate, and therefore, his withholding consent based on his right not to be physically harmed contradicts his aggressive legitimation of force.'