Cursus Philosophicus Thomisticus, Secunda Pars Artis Logicae

Almost the whole DIFFICULTY of this article depends on understanding the terms stated in its title.

First, we are speaking of the art of Logic, that is, artificial Logic, not natural Logic. Natural Logic is nothing other than natural light itself using reasoning. This natural light is not the intellect's bare potency, but the intellect together with the habit of principles that are naturally known. Yet those principles are not the science or art itself; the habit of principles and the habit of an art or science are very distinct habits. When we inquire into the necessity of Logic, there is no difficulty about Logic's principles or the habit of its principles, which some abusively call preceptive or actual Logic, since this is not Logic but its principle.

Second, by “science” one may mean science only in substance, in an imperfect state, as science is generated in substance in the first demonstration—that is, by convincingly and certainly and evidently persuading the intellect. Or one may mean science in its perfect state, which simply denominates someone a knower: the science by which the intellect is not only convinced but can also reason on its own about what pertains to full knowledge of that science's object, and defend itself against contrary errors or attacks. In the present inquiry into Logic's necessity for science, “science” may be taken in either sense.

Third, the title asks whether Logic is necessary without qualification. Here “necessary without qualification” does not mean “absolutely necessary,” which is taken from the side of an intrinsic cause, whether matter or form, as it is necessary for a human being to be rational and mortal. Rather, it means necessary with reference to something else, that is, to the attainment of some end. Necessity for an end is said in two ways: something is necessary without qualification or necessary in a certain respect. It is necessary without qualification when required for the very being of a thing, either to acquire or to preserve it, as food and breathing are required for living. It is necessary in a certain respect when required for well-being, that is, for some greater convenience or adornment, not for being itself as such. On these divisions of absolute and relative necessity, and of necessity without qualification and in a certain respect, see St. Thomas, Metaphysics V, lect. 6¹.

Since no one doubts, then, that Logic is at least useful and necessary in a certain respect—that is, for the sciences' better and more convenient condition—the whole difficulty reduces to whether Logic is necessary without qualification.

RESOLUTION.

LET THERE BE ONE CONCLUSION: Artificial Logic is necessary without qualification for the speculative sciences with respect to science's perfect state and its preservation and, as it were, nourishment; it is not necessary with respect to science's imperfect being and its first generation, as it were.

Thus it can be called necessary without qualification, with no further qualification, but not necessary without qualification in every way. Breathing and food, for example, are said to be necessary without qualification for an animal, not because they are required in every way and in every state. In the mother's womb, when an animal is first generated, it needs neither food nor breathing. Nevertheless, these are called necessary without qualification for an animal because they are required not for some added adornment or benefit, but for the animal's very being—not for its initial generation, but for its preservation and nourishment.

We say that Logic is necessary for the speculative sciences, not for the practical sciences, because practical sciences concern only the rightness of an operation, internal or external, and not the investigation of truth itself. Hence they need only prudence or art, which direct the goodness or rightness of things to be done or made, not Logic, which directs only the rightness of reasoning about truth.

By this conclusion we reconcile the opposed opinions concerning Logic's necessity. Some think Logic is only useful and not necessary without qualification, such as the Coimbra commentators, Prooemium, q. 6, art. 2, and others; others think it is necessary without qualification in every way, just as a universal cause is required without qualification for every action of a particular cause, such as Araujo, Metaphysics II, q. 3, art. 3, and others.²

We say, however, that Logic is necessary without qualification, speaking absolutely, but not in every way and in every state of any science. For something can be said to be such without qualification either because it is such absolutely and without an addition, or because it is said to be such in every way and under every consideration, as St. Thomas aptly observes in Summa theologiae III, q. 50, art. 5. What is such without qualification in the first sense admits of some latitude, and can be called necessary or such without qualification even though it is not necessary in every way and in every state. On this conclusion see the Carmelite Course, introductory disputation, q. 7.

THE FIRST PART, then, of the conclusion—that Logic is not necessary without qualification, that is, in every way, for the other sciences—is clear from this: Logic is required for the other sciences only as an art and instrument for acquiring them. The effect of an art does not depend on the art in such a way that it cannot be produced in some manner, at least imperfectly, without it. As the Philosopher says, “a person learning an art performs an action of the art without the art.”³ St. Thomas explains this at the end of his lecture 7⁴: “a person can in some way enter into an act of science and virtue before having the habit of science and virtue; once that habit has been acquired, he acts perfectly.” Indeed, if this were not so, the arts and sciences themselves could not be acquired through our acts, since at least the first acts by which they are acquired cannot proceed from the art, given that they generate it. Likewise, some demonstrations do not necessarily depend on Logic, at least those that generate Logic's first demonstration. Although those demonstrations do not exist without the Logic generated through them, Logic is not required for them; rather, they give rise to it. And if a demonstration is made in the subject matter of another science, it can be grasped and convince the intellect of someone who does not possess Logic. That person will then acquire the habit of the science to which the demonstration belongs, but not the habit of Logic, whose precepts he is not then being taught.

Finally, for this part we should consider St. Thomas's teaching in Metaphysics VII, lect. 8⁵, Summa theologiae I, q. 117, arts. 1 and 2, and Against the Gentiles I, chapter 75. There he distinguishes two kinds of art: “In some materials there is no active principle that produces the effect of the art: wood and stones, for example, have no active power moving them toward the construction of a house, which is the effect of the house-building art. Sometimes, however, an art works in material that has a moving principle for producing the art's effect, as is clear in medicine, because in a sick body there is an active principle for health. Nature never produces the effect of the first kind of art; it is always produced by art. But the effect of the second kind is produced by art and sometimes by nature without art.” So St. Thomas. Since Logic concerns directing the intellect's operations, and the intellect contains a moving principle for proceeding scientifically, just as the body contains a principle for health, an effect of Logic's art can sometimes be produced without the art. Thus Logic is not necessary without qualification for every demonstration and science, in every state and manner.

THE SECOND PART, namely, that Logic is required without qualification for science's perfect state and its preservation, is drawn from St. Thomas. In On Boethius's De Trinitate, q. 6, art. 1, second question, ad 3⁶, he says that necessity requires us to begin learning with Logic, although it is not easier than the other sciences, because the other sciences depend on it. And in Metaphysics II, final lecture⁷, and Posterior Analytics I, lect. 1⁸, he says Logic is ordered toward proceeding easily, promptly, and without error. It is clear that proceeding without error is not merely useful but necessary without qualification for the very being of the other sciences. It is also clear that the intellect's bare potency, unaided by art, cannot recognize every defect in inferences or scientifically discern the soundness of any inference, since many things are not known by natural light but are gathered by reasoning. Many things concerning knowledge of propositions that are per se and of necessary connections also depend on Logic's principles and precepts: for example, knowledge of the categories, in which essential predicates are arranged; of the predicables, which set out the modes of essential and accidental predication; and of the modes “per se,” “of every,” and “according to itself,” along with other matters taught in the Prior Analytics and Posterior Analytics. On these depends the discernment of necessary or contingent matter and of valid or defective inference. Therefore, the intellect cannot reach science's perfect state, in which it avoids all these errors and extends to its various conclusions, except through some principle added to it that teaches this artful mode of proceeding. Just as an animal in its perfect state—that is, when it nourishes and increases itself—needs food as the matter of nourishment, and digestion and assimilation of food, so for the nourishment and extension of the sciences, which must take place through many conclusions and various inferences, the intellect needs food, namely, species, but species that have been digested, assimilated, and arranged artfully for inference; otherwise it will not draw conclusions scientifically. The art of Logic provides this.

YOU WILL SAY: This is not necessary for being without qualification, but for better or more perfect being, because the being of the sciences is presupposed, just as the being of an animal is presupposed by food, which is required only for something added to the animal's being. Therefore Logic is not necessary without qualification, that is, for being.

The reply is that although Logic presupposes being, it is not said to be required for something added to being and, as it were, extrinsic to it, but for the continuation and preservation of being itself, so that it is not lost. For something to be required for a thing's being, and not for something added to it, is sufficient for its being necessary without qualification, even if it is not required for every state of that being. Food, for example, is not required for a human being's being during generation, but it is required for its preservation.

THE OBJECTIONS ARE ANSWERED.

First it is argued: Many demonstrations can be made without Logic; therefore Logic is not required for science's being, even in its state of preservation.

The antecedent is proved: many conclusions in a science can be demonstrated by the four moods of the first figure, which are known by natural light itself and not through the reasoning of Logic's art, since other conclusions are reduced to them as principles. It is also clear that Logic itself was first learned by natural light, without some earlier acquired Logic. Therefore the art of Logic is not required for science's very being, even as it extends to more conclusions, which is its perfect state.

THE REPLY: The antecedent is denied. Anyone who forms demonstrations without Logic, even if he does so in the four first moods of syllogizing, is always said to have science in an imperfect state, because without Logic one cannot arrange the several matters and conclusions of a science so clearly as to reduce them all to the first moods of syllogizing. Indeed, to perform this task one must be most perfectly practiced in the science and especially well versed in Logic's precepts. Nor can one similarly defend oneself against oppositions by discerning defects and weaknesses in the inferences used to attack one, or defects in definitions and divisions, and so on. Without this, however many demonstrations are made, they always remain in a weak and imperfect state. Logic itself, when first discovered, was discovered imperfectly by natural light, as were all the other arts. Later, in its perfect state, it helps itself and preserves itself just as it helps the other arts; thus no other Logic is necessary, because Logic suffices for itself.

Second it is argued: Natural light itself has sufficient power to acquire any demonstration taken separately; no final demonstration can be identified beyond which it is unable to proceed. Once a demonstration has been acquired, natural light's power is not diminished but rather increased. Therefore it will be able to proceed to a second and all the others without Logic, although less conveniently.

THE REPLY is that in arguments which move from a divisive enumeration of things a power can do to a complete and integral enumeration, a fallacy of accident or a defect of supposition is commonly committed. Each operation is counted separately, while the mode of operating through continuation and extension from one thing to another, and defense against opposing views, is omitted. Yet the whole collection is inferred, and that collection includes this mode of continuation or extension even though it was not counted. This cannot be done by limited powers unless they receive help from elsewhere. Although the intellect's power is not diminished by making one demonstration, because of its limitation it cannot continue all these operations and defend itself against opposition unless aided by some art. Thus, even though this enumeration seems to be made conjunctively by the word “and”—saying, “It can do this and it can do that,” and so on—in sense it is disjunctive. To be able to do this separately and divisively, and that separately, is the same as being able to do this or that disjunctively or divisively. But a distributive conclusion cannot be drawn from a disjunctive enumeration. For this reason we do not identify a single point beyond which the intellect cannot proceed separately and divisively. Rather, in this enumeration the limit it cannot reach is the whole collection, or the entire range of perfect power; it cannot reach that, although it can reach the imperfect or divisive range.

Finally it is argued: Logic contributes an artful mode of proceeding to all the sciences, as is clear from the Philosopher in Metaphysics II⁹, St. Thomas there, final lecture¹⁰, and Metaphysics IV, lect. 4¹¹. Therefore Logic is related to all the sciences as a universal cause. But a universal cause is required without qualification for every operation of a lower cause, just as if the motion of the heavens ceased, all lower motions would cease. Therefore Logic is required without qualification, that is, in every way, for every artful demonstration. If any demonstrations are made without Logic, they will not be artful or resolved up to the first principles.

THE REPLY is that Logic is not a universal cause primarily and in itself, but an instrument assisting the principal agent, which is the intellect. St. Thomas teaches this about every art in Summa theologiae I, q. 117, art. 1. An instrumental universal cause is not necessary without qualification in such a way that no effect of art can be produced without it, especially when that instrument is virtually contained in the principal cause itself and is derived from its principles. In place of the instrument, therefore, the principal cause can make up for the art's deficiency and produce the art's effect without the art. The heavens, however, are not a cause in the manner of an art or instrument, but a principal and universal cause, though moved by another, higher cause. As for the added point about resolution to first principles, the reply is that some resolution to first principles and some soundness of inference can be so per se evident that it can be grasped without art, although only in the imperfect state described above. All the other arts and sciences likewise had an imperfect state when they were first acquired.