Cursus Philosophicus Thomisticus, Secunda Pars Artis Logicae

Science can refer either to actual science or to habitual science. It was defined in the first sense above¹, when the Philosopher says that “to know is to know the cause on account of which a thing is, and that it is the cause of that thing, etc.” Habitual science is usually defined as a habit acquired through demonstration, just as, conversely, demonstration was defined² as a syllogism that produces knowing. This is not circular: demonstration is not said to be a syllogism that immediately produces the habit of science, but one that produces actual knowing—that is, scientific assent—from which the habit is generated and which inclines one to similar assent. Moreover, demonstration was not defined by that definition alone, but also by another; having thus been made known in another way, it could again be used to define science without circularity. Second, the habit of science can also be defined as “a habit that concerns a conclusion known from universal, necessary, and immediate propositions.”

To understand the account of science better, we must discern the DISTINCTION BETWEEN IT AND THE OTHER INTELLECTUAL HABITS. Here we shall treat evident habits; later, the non-evident ones. St. Thomas briefly numbers them all in the Posterior Analytics, I, final lecture.³ “We should know,” he says, “that Aristotle, in Ethics VI,”⁴ “posited five that are always directed toward truth: art, science, wisdom, prudence, and intellect. He then added two that are directed toward both truth and falsity: suspicion and opinion, to which human faith is also reduced. The first five are directed only toward truth because they imply rightness of reason. Three of them—wisdom, science, and intellect—imply rightness of cognition concerning necessary things: science concerning conclusions, intellect concerning principles, and wisdom concerning the highest causes. The others imply rightness of reason concerning contingent things.” So says St. Thomas, who treats this subject more fully in Summa Theologiae I–II, q. 57, and in his commentary on Ethics VI.

Accordingly, those five habits agree in that they are intellectual virtues, because they dispose the intellect rightly toward truth. Its disposition is right when the intellect proceeds firmly and with certainty: if it is not yet firm in truth but can lapse into falsity, it is not yet perfected in regard to truth, but is imperfect and defective. A virtue, however, is a perfect disposition. Hence there can be no intellectual virtue unless it is a certain habit concerning truth. These habits begin to differ from one another because some order the intellect toward practical truth and others toward speculative truth. Prudence and mechanical art concern what is practical; they direct contingent things—that is, art directs things to be made, and prudence things to be done. We need not treat these here.

Among the three remaining habits, which concern the speculation of necessary truth, intellect comes first: it is the principle of the others and is therefore called the habit of principles. Some have thought that it is nothing other than the intellectual power itself, which is determined by itself, without any added habit, to assent to principles—just as the will, a power, is inclined to love itself and the good in general without an added habit. See the Cursus Carmelitarum, disputation 20, q. 1, on these matters. The opposite must instead be assumed as certain, as St. Thomas assumes in Summa Theologiae I–II, q. 57, a. 3, and in his commentary on Nicomachean Ethics VI, lecture 5.⁵ There he says: “Intellect is taken not for the intellectual power itself, but for a certain habit by which a human being naturally knows indemonstrable principles by virtue of the light of the agent intellect. The name is quite fitting: principles of this kind are known immediately upon knowing their terms. Once one knows what a whole is and what a part is, one immediately knows that every whole is greater than its part. It is called intellect because it reads within by looking into the essence of a thing. Thus the cognition of principles, which become known immediately when what a thing is has been grasped, is aptly called intellect.” So says St. Thomas.

His words plainly establish the reason for distinguishing the habit of principles from the intellectual power: the power is not in itself a determinate light but is indifferent to every truth, like a blank tablet in its initial state. In becoming determinate, it depends on the light of the agent intellect, through which the intellectual power is perfected by determinate species for determinate truth. Since the habit of principles cannot make its objects or principles manifest to the intellect except in dependence on these determinate species, a light that makes the principles manifest must necessarily be added to the intellectual power. In itself, the power is not a light that manifests a determinate object, since it lacks every species from which such a light proceeds; rather, it is capable of, or receptive of, a light made determinate by the agent intellect through species. The habit of principles thus arises on the supposition that the species make things manifest, since it concerns determinate objects.

This resolves the example concerning the will that was given. The will does not receive its inclination toward the good in general or its proper good through species added to it; rather, it is inclined by itself, or is itself an inclination toward a fitting good. An inclination, by its nature, follows some form; it is not perfected by a form that represents it, as the intellect is perfected by an added form, the species of its object. If the form that the inclination follows is a proper good that naturally suits it, the inclination follows naturally, and it needs no habit to be directed toward that good. If the good is indifferent and not fitting in a fully determinate way, the will needs a habit to establish the determination appropriate to that indifference. None of this applies to the habit of principles, which belongs to the intellect on the supposition that the terms have been explained.

From this it follows that the habit of principles is not created together with the power itself, as some have said, nor is it innate by nature; rather, it is acquired through the light of the agent intellect, on the supposition of the impression of species abstracted from the senses, as St. Thomas expressly teaches in Summa Theologiae I–II, q. 53, aa. 1–2, and Summa contra Gentiles, I, chap. 78. We need not discuss it further here, since it does not belong to the logician’s task.

If you ask whether there is one habit with respect to all principles, the answer is that principles—that is, propositions lacking a middle term—can be found either in necessary matter or in probable matter. For even among probabilities there are certain first principles and immediate propositions, as we shall show below from Aristotle, Posterior Analytics I, chap. 26,⁶ and St. Thomas in the same place, lecture 44.⁷ Similarly, some principles are speculative and others practical; among speculative principles, some are most common and are called axioms, while some are particular and are called suppositions; there are also the quidditative definitions found among the subjects of the sciences.

I SAY, THEREFORE: Habits of probable principles differ from the habit of evident principles, and likewise habits of practical principles differ from speculative ones.

St. Thomas speaks of them as distinct habits in the cited question 53. The habit of practical principles is called synderesis, while that of speculative principles is called intellect. All speculative principles, however, whether axioms or suppositions, belong to the same habit.

THE REASON FOR THE FIRST PART is that probable and evident light always differ essentially. The evident and the non-evident, the necessary and the contingent, are opposed to one another; therefore they cannot be grasped by the same light. For the same reason, practical principles cannot belong to the same habit as speculative ones. Practical certainty is perfected by moral certainty, according to moral and prudential fittingness, which tends toward and applies to contingent actions that it inclines us to perform, such as acts of the will and works produced by art. For although practical principles are ultimately resolved into certain necessary truths in general, insofar as they are practical they include contingency in particular. Consider the principles “Good is to be done” and “God is to be worshipped.” In general, and in a manner of speculation, they are resolved as follows: “The account of the good itself requires, or makes it fitting, that it be done”; “worship is due to God.” In practice, however, they direct particular action by way of command or counsel: “It is fitting for you to do this good, to worship God, etc.” In this kind of direction and in making a fitting judgment, these are first principles, because they immediately show what is prudentially fitting by the terms alone. That something is prudential and fitting is necessary simply; that it practically moves and brings about an act, however, is contingent and morally certain.

THE REASON FOR THE SECOND PART is that all first principles, whether they are most common or less common, share the same formal account of assent: assent without a proving middle term, once the terms alone have been explained. The fact that the terms are more or less known to us and more or less common, and so constitute more or less common principles, pertains only to how easily and commonly the terms can be explained. Once they have been explained, it does not amount to a different mode of assent.

As for the difference between the habit of wisdom and that of science, note only what St. Thomas says in Opusculum 70, q. 2, a. 2, ad 1⁸: “Wisdom is not divided against science as one opposite against another; rather, it stands to science by way of addition. For wisdom, as the Philosopher says in Nicomachean Ethics VI, is the head of all the sciences, regulating all the others because it concerns the highest principles.” Accordingly, wisdom’s task is to judge and to resolve through ultimate causes or first principles, as St. Thomas also teaches in Summa Theologiae I–II, q. 57, a. 2, and I, q. 1, a. 6. Because the principles from which it proceeds are universal, wisdom also reflects on its own principles and those of the other sciences—not to prove them, but to explain and defend them. For this reason wisdom is said to include intellect and science, since it also extends to principles whose habit is called intellect. Wisdom is truly an inferential habit, however, using inferential proof and proceeding from principles; therefore it belongs to the order of the sciences.