Cursus Philosophicus Thomisticus, Prima Pars Artis Logicae

At the very threshold of the art of Dialectic, which we undertake to explain according to our limited ability, it has seemed good to set before beginners, in the very exercise and practice, the form and manner of disputation, which can be explained briefly as follows.

Therefore, in any disputation, let the one who argues take care first to propose the argument, reduced entirely to form, with everything else cut away, whether verbal circumlocutions or lengthy explanations; and let him set forth the syllogism or enthymeme succinctly and distinctly. A syllogism contains three propositions, called the major, the minor, and the conclusion or consequent, connected by the sign of inference, namely the particle “therefore”; the connection itself is called inference or consequence. An enthymeme, however, contains two propositions, the first of which is called the antecedent and the second the consequent, connected in the same way. For example, if I intend to prove that a life of pleasure is not to be embraced, I form a syllogism thus: “Whatever is opposed to the moral integrity of virtue is not to be embraced; a life of pleasure is opposed to the moral integrity of virtue; therefore it is not to be embraced.” Or, if I wish to form an enthymeme from an antecedent and consequent, I form it thus: “A life of pleasure is opposed to the arduousness of virtue; therefore it is not to be embraced.”

After hearing the proposition of the argument, let the respondent attend to nothing other than repeating the proposed argument completely and faithfully; meanwhile, as he takes up the argument again, let him consider whether any premise is true, so that it may be granted, or false, so that it may be denied, or doubtful or equivocal, so that it may be distinguished; and likewise whether the consequence or inference is good or bad. Having once taken up the argument again without responding to it, let him repeat it a second time and answer each proposition in this order. If there are three propositions and he sees that the first is true, let him say: “I grant the major.” If he sees that it is false, let him say: “I deny the major.” If he sees that it does not pertain to the conclusion to be inferred, let him say: “Let the major pass”—though this expression should be used modestly and sparingly, and only when it is clear that the proposition is irrelevant. If he sees that the major is doubtful or equivocal, let him say: “I distinguish the major,” and make the distinction briefly and clearly concerning the term in which the equivocation lies. Once the distinction has been given, let him not explain it at once unless the opponent asks him to, or unless it was not stated clearly enough; in that case let him explain it very briefly. Especially at the beginning of a disputation, let him not spend time explaining distinctions, but never depart from the form itself. Once the major has been granted or explained under a distinction, let him proceed to the minor and observe the same procedure in denying, granting, or distinguishing, as we said concerning the major. Then, coming to the conclusion, if it is to be granted, let him say: “I grant the consequence”; if it is to be denied, “I deny the consequence.” But if it is to be distinguished, let him not say “I distinguish the consequence,” but “I distinguish the consequent.” For the consequence, since it consists in the inference itself and not in an assertion of truth, can be a good or bad inference, and thus be granted or denied as good or bad, but it cannot be distinguished; for a distinction applies to the equivocation or ambiguity of a proposition, insofar as it has different senses in signifying truth, not to the validity of the inference itself. The consequent, however, is the proposition inferred, which may be certain, equivocal, or ambiguous; hence, when it is equivocal, it is distinguished, and so one does not say “I distinguish the consequence,” but “I distinguish the consequent.” If, however, the consequent is to be granted or denied—for this can be done only by granting or denying the consequence itself—it is enough to say “I deny the consequence” or “I grant the consequence,” not the consequent.

Once a distinction has been made concerning a proposition, whenever the same equivocation occurs, let him apply the same distinction. Let him not subdivide a sense of a distinction once granted, unless another equivocation clearly appears that could not be removed by the prior distinction. Whatever is false, it is safer to deny, and not to let pass, unless the invalidity of the consequence is certain. If he does not grasp the sense of a proposition well enough to discern its truth, falsity, or equivocation, let him ask the one arguing to explain its sense, and then take it up again.

Finally, let him take care to answer briefly and to bind himself only to the form of the argument; let him not undertake to give an account of everything he says unless asked, but leave the entire burden of proving the argument to the other. For in this way the formal force of the argument becomes clear and it is dispatched more quickly.

It belongs to the role of the one who argues: first, not to put forward many presuppositions, insist on many middle terms, or propose propositions that are too long or involved, but to keep succinctly to the form; not to use many questions, but rather to press the proofs—except when the force of the argument turns on asking for the reason for what has been said, or when the state of the disputation and the point of difficulty have not yet been sufficiently clarified. Second, let him always pursue the same middle term through its causes and principles, or by deriving an absurd consequence; let him not turn aside to another middle term, nor repeat a proof once proposed, either in the same words or in others, since both are very prolix and tedious. Finally, let him not always use a syllogism, but sometimes an enthymeme, which proceeds more briefly and concisely and reveals less of the force of the latent inference, and therefore makes the task more difficult for the respondent.

Finally, it belongs to the role of the moderator or presiding officer: first, to grasp attentively the entire progress of the argument and disputation; second, to ensure that the form of arguing and responding is observed completely; third, not to assume or anticipate the respondent’s role, much less the opponent’s, but prudently, as he sees the respondent needs, to suggest denial, concession, or distinction of the proposition. Finally, at the end, he should give a brief judgment on the disputation and clarify what is obscure.