The Art of Scholastic Disputation

It seemed best to show beginners the form and procedure of disputation in actual use and practice. It can be briefly described as follows.

In any disputation, the first concern of the one arguing should be to propose an argument entirely reduced to form. That is to say, having stripped away everything superfluous, whether ambiguous words or lengthy declarations, the one arguing should succinctly and distinctly propose a syllogism or an enthymeme. A syllogism contains three propositions, which are called the major premise, the minor premise, and the conclusion or consequent, connected by the sign of illation, which is the particle "therefore." The connection itself, however, is called the illation or consequence. An enthymeme contains two propositions, of which the first is called an antecedent, the second a consequent, also connected by an illation. For example, if I want to prove that one ought not embrace a life of voluptuousness, I form a syllogism thus: "Whatever opposes true human virtue ought not to be embraced; a voluptuous life opposes true human virtue; therefore it ought not to be embraced." Or, if I wish to form an enthymeme of antecedent and consequent, I form it thus: "A voluptuous life is opposed to the arduousness of virtue; therefore it ought not to be embraced."

Hearing the formulation of the argument, the one responding should attend to nothing except to repeat integrally and faithfully the argument proposed, and meanwhile, while he repeats the argument, he should consider carefully whether each premise is true, and to be granted, or false, and to be denied, or doubtful or equivocal, and to be distinguished. He should likewise consider whether the consequence or illation is valid or invalid. Having repeated the argument once without saying anything by way of response, the one responding then should repeat and respond to the propositions of the argument taken singly, in this order: If there were three propositions and he things the first to be true, he should say: "I grant the major premise." If he things it false, he should say: "I deny the major." If he thinks it does not matter for the conclusion that ought to be inferred or drawn, he should say: "Let the major pass," although this formula should be used modestly and rarely, and not unless it is clearly the case that the proposition is irrelevant. If he thinks the major is doubtful or equivocal, he should say: "I distinguish the major," and make the distinction with few and clear words, based on the term in which there is an equivocation. Having made the distinction, he should not immediately explain it, unless either the opponent asks for an explanation, or [he himself sees how] it was not expressed clearly enough, in which case he should explain it as briefly as he can. Especially at the beginning of a disputation he should not use up time explaining distinctions, but should in no wise depart from the form itself of his argument. When the major has been granted or explained under a distinction, he proceeds to the minor premise and observes the same procedures in denying or conceding or distinguishing that we we have set out for the major premise. Then, coming to the conclusion, if it must be conceded, he says: "I grant the consequence." If it must be denied, he says, "I deny the consequence." But if the conclusion must be distinguished, he should not say, "I distinguish the consequence," but rather, "I distinguish the consequent"; for since the consequence consists in the illation itself, but not in an assertion of truth, it can be a valid or an invalid illation, and so can be granted or denied as valid or invalid, but it cannot be distinguished, because a distinction falls upon an equivocation or ambiguity in a proposition so far as the proposition has diverse senses in signifying a truth, not upon the correctness itself of an illation. The consequent, however, is the illated [or inferred] proposition, which can be certain or equivocal or ambiguous; whence, when it is equivocal, it is distinguished, and so one does not say "I distinguish the consequence," but "I distinguish the consequent." Yet if the consequent is to be conceded or denied, since this cannot be done except by conceding or denying the consequence itself, it suffices to say "I deny (or I grant) the consequence," but not to say, "I deny (or I grant) the consequent."

When a distinction has been made respecting some proposition, that same distinction should be applied as many times as the same equivocation occurs. One should not subdistinguish the sense of a distinction once that distinction has been granted unless another equivocation plainly appears which cannot be removed by the prior distinction. It is safer to deny whatever is false and not permit it to pass, unless it is certainly a case of an invalid consequence. If the one responding does not grasp the sense of the proposition, and so is unable to discern truth or falsity or equivocation, he should ask the one propounding the argument to explain its sense, and then he should repeat the explanation.

Finally, the one responding should take care to answer with few words, and to be bound only by the form of the argument. Nor should he give a reason for everything he says, unless a reason is asked of him. He should rather leave to the one arguing the entire burden of proof; for in this way the force of the argument becomes more formally clear, and it is the more quickly dispatched.

It is the part of the task of the one presenting the argument: First, not to lay down many presuppositions, nor to introduce many middle terms, nor to propose excessively long or intricate propositions, but to hold succinctly and stringently to form, not by asking many questions, but rather by setting forth proofs, except when the force of the argument devolves upon this, that he is asked a reason for the things said, or when the state of the disputation and the point of the difficulty have not yet been made sufficiently clear. Second, to proceed always with the same middle term through its causes and principles, or in deducing an inconsistency, but not to switch to another middle term, or to repeat a proof already proposed either in the same or in other words, because both are unduly wordy and tedious. Finally, he should not always use a syllogism, but sometimes an enthymeme, which proceeds more briefly and concisely and manifests less force of hidden illation, and for this reason presents a greater difficulty to the one responding.

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Source: John of St. Thomas, Tractatus de Signis, ed. Deely (South Bend, IN: St. Augustine's Press, 2005), 1.1, 10-12.