Cursus Philosophicus Thomisticus, Secunda Pars Artis Logicae

Authors speak variously and obscurely about this distinction between logic as teaching and logic as being used. Logic is called teaching insofar as it teaches scientifically the rules for directing the intellect; it is called being used insofar as it puts those rules into execution in this or that subject matter. This division of logic into being used and teaching was adopted because, just as the things that direct practical activities both hand down rules and have a use, so logic, which directs speculative activities, has these two.

AND THE REASON FOR THE CONTROVERSY is reduced to two points. The first concerns the matter: whether use and teaching in logic deal with the same matter, whether demonstrative or opinionative, or only with topical matter. The second concerns the form: whether the teaching and use of logic belong to the same habit and formal principle.¹

To clarify this obscurity, we need note just one thing from St. Thomas’s teaching: A THREEFOLD USE OF LOGIC can be distinguished. The first is its provision to the other sciences of a way to proceed artfully by syllogistic form. For it belongs to logic to provide the other sciences with a way to proceed so that they do not err, and to direct the works of reason by furnishing instruments of speculation, as St. Thomas teaches from the Philosopher in Metaphysics II, final lecture,² Opusculum 70, q. 5, a. 1, ad 2,³ and Posterior Analytics I, lecture 1,⁴ and often elsewhere.

The second use belongs to logic as teaching, when it provides other sciences not only with syllogistic form but also with principles for deriving certain proofs, just as other sciences too are assisted by others through taking up their principles, especially from metaphysics. St. Thomas teaches that this use belongs to logic in Opusculum 70, q. 6, a. 1,⁵ where he says that sometimes we use logic as teaching in the other sciences because it provides them with certain principles for proving, as when we prove something in the other sciences from the notions of genus, species, or opposition. In Posterior Analytics I, lecture 20,⁶ he gives an example: “We prove,” he says, “that love and hatred belong to the concupiscible power because contraries concern the same thing; this proof is taken from a logical principle, namely, the nature of contrariety.”

The third use of logic is its most proper one: it provides a way of disputing probabilistically in other sciences or subject matters without proceeding demonstratively and resolutively all the way to first principles. In this case logic is properly called logic being used, as distinguished from demonstrating and teaching, because the demonstrator does not merely use reasoning and stop there, but reaches first principles by resolution; these are not proved by reasoning but are its endpoint. Logic being used does reason, but without demonstrating: it uses reasoning and stops there without reaching the endpoint of reasoning, which is resolution to first principles. This belongs to the disputative or tentative procedure, in which one proceeds by inquiry rather than resolution. It is therefore called a probable procedure, because it does not reach the principles with the certainty of a final resolution. This is the act of logic being used,⁷ and St. Thomas explains it in Opusculum 70, q. 6, a. 1,⁸ saying that logic being used is that which uses reasoning but not its endpoint, which terminates in self-evident principles, where the use of discursive reason ceases.

With these points established, it is certain that logic being used, when “use” is taken in the first or third sense (for the second belongs to logic as teaching, since furnishing its principles to others so that they may demonstrate pertains to the exercise of teaching), is not formally called a science. In the third sense, this is because it proceeds only probabilistically or disputatively, not resolutively. In the first sense, it is because that use of logic is not demonstration, which alone confers the name of science, but an application and concurrence that arranges syllogistic form, whether in demonstrative or topical matter; hence it is not a determinate use of science and demonstration. As for the difficulties raised, however—

I SAY FIRST: Logic being used, when use is taken in the first sense, must direct not only the topical part but also the demonstrative part—and indeed especially the latter.

We use the word “direct,” although some in this sense call it not logic being used but logic directing, so that we may avoid a dispute over the name. For the use of logic in this respect is direction, just as the higher sciences and architectonic arts have as their proper act or use the directing of lower ones.

This conclusion is taught by St. Thomas, first, in Posterior Analytics I, lecture 1,⁹ where he says that not only the other works of reason, but especially its judging or demonstrative part, is directed by logic. Second, he teaches that logic supplies instruments of speculation to all sciences—which certainly proceed demonstratively—in Opusculum 70, q. 5, a. 1, ad 2,¹⁰ and in Metaphysics II, final lecture,¹¹ he teaches how logic provides every science with a method of knowing. Therefore the use of logic must not be restricted here to the topical part alone, but extends also to the demonstrative part.

THE REASON IS clear: demonstration requires the structure of a syllogism and the goodness of a consequence, regulated according to logical rules and principles, no less than other probable syllogisms do. Therefore the arrangement and artful form in demonstrations derives from logic. It depends on logic’s principles and rules both with respect to form, which is regulated by “said of every” and “said of none” and by other principles that arrange the syllogism, and with respect to matter, because demonstration must use necessary and per se propositions, which logic especially considers in resolutive reasoning of the Posterior Analytics.

It is no objection that, even when rightly arranged, these demonstrations proceed effectively from the particular sciences that arrange the syllogism, while they depend on logic only for direction. I say this is no objection because we are not now determining that logic influences demonstrations in the other sciences by effectively eliciting them; it is enough that it influences them by directing them, just as prudence influences the virtues not by eliciting their acts but by commanding them. Or, if logic does influence them effectively, its influence is not that of a principal cause demonstrating, but of an assisting and furnishing cause. Virtues elicit a moral act regulated by prudence, whether that mode of regulation in the acts of the virtues is effectively caused by prudence through a real impression in the moral virtues or only by direction; this does not pertain to the present question, but to the question whether the command of a superior power or virtue over the lower powers it moves occurs through an effective impression. Whatever the answer, it is clear that with respect to an opinionative and probable syllogism as well, logic influences its syllogistic arrangement no more effectively and elicitingly than it does a demonstrative syllogism, but only by direction. We say that logic has this same direction or use in a demonstrative syllogism.

I SAY SECOND: Logic being used, taken in the third sense, deals only with the topical and sophistical part, that is, with a procedure that is not resolutive but probable, probative, and disputative. If such use takes place in other sciences from the principles of those sciences, disputing from them without resolution, that use belongs to logic only as directing. But if such a non-resolutive disputation proceeds from logic’s own principles, it will belong to logic not only as directing but also as eliciting, like a secondary and imperfect act.

St. Thomas intends this conclusion in Metaphysics IV, lecture 4,¹² when he says that “logic, insofar as it is teaching, considers these logical intentions, establishing a method by which one can proceed probabilistically through them in the several sciences, and thus it is a science. But it is being used insofar as it uses this method in order to conclude something probabilistically in the several sciences, and thus departs from the method of knowing.” St. Thomas teaches this more explicitly in the cited Opusculum 70, q. 6, a. 1,¹³ where he says that “a rational procedure is sometimes named from the endpoint at which it stops while proceeding. The ultimate endpoint to which reason’s inquiry must lead is understanding of the principles, into which we judge by resolving; when this happens, it is called demonstration. But when reason’s inquiry does not reach the ultimate endpoint, but stops in the inquiry itself—when, that is, the inquirer still has a path open either way—then rational procedure is distinguished from demonstrative procedure. One can proceed rationally in this way in any science, so that a path to necessary conclusions is prepared from probable things. This is another way in which logic is used in the other sciences, not as teaching but as being used.” Thus St. Thomas.

Taking logic being used in this sense, it is clear that it does not pertain to the demonstrative part but to the topical part, because such use is not demonstration: it is not resolution with full determination to certain and evident principles, but proceeds only by inquiry and disputation toward either alternative. If it does so by providing principles proper to that reasoning and disputation, logic elicits the whole procedure, because it provides not only the method of disputing but also the matter or principles. Whatever a habit derives from its own principles and object belongs to that habit elicitingly, whether the derivation is resolutive or only disputative. But if the procedure or disputation is formed from principles of other sciences or habits, then logic provides only the method of disputing—that is, it provides direction, not the eliciting of the act in its substance.

I SAY FINALLY: The habit of logic as teaching and as being used is the same, whether it directs or elicits, disputes probabilistically or proceeds demonstratively; and the specific formal rationale of each is the same.

Not everyone agrees with this conclusion. Some take one extreme and say not only that logic being used and logic as teaching are the same habit, but that the very same act both uses and teaches; this is Martínez’s view here, q. 2. Others take the opposite extreme and posit not only distinct acts but distinct habits as well, because they say that logic as teaching is speculative and logic being used practical, as Vázquez does in part I, disp. 8, ch. 5, no. 19; or because they say the teaching habit is scientific, while the habit of use is opinionative, as some cited by the Coimbra commentators, q. 4, proem, a. 2. Others say that logic as teaching and being used is the same habit in the matter and object proper to logic, but that in other sciences the user is not the habit of logic; rather, it is the habit of those other sciences itself that produces its inferences in an orderly way. So Master Cabero, disp. 2, proem, doubt 2. Father Merinero here, q. 2, section 2, does not in substance depart from him: he distinguishes the habit of logic being used elicitingly from the habit of logic as teaching; when it deals with the matter of other sciences, he says, that eliciting belongs to the habits of those sciences.

Nevertheless, the proposed conclusion, stated absolutely and without so many distinctions, is more common among authors, and especially among Thomists. On this point one should consult Flandricus, Metaphysics II, q. 5, a. 2, ad 2; Master Araujo there, q. 3, a. 2; Master Soto, Sánchez, Masius, and the Carmelite Course, disp. 1 (proem), q. 4, § 2.

THE REASON IS that the other sciences do not have within themselves principles that order their inferences; rather, they borrow them from logic, which hands them down and explains them. Therefore they elicit ordered consequences only through the power of logic, or through the light communicated to them at least by direction and by presentation of the object. Thus St. Thomas continually teaches, especially in Opusculum 70, that logic furnishes the other sciences with instruments of speculation. Logic itself teaches the method of speculating and uses it through the same habit, because in any subject matter it uses and applies the same principles by which it hands down its teaching to form consequences; it requires neither a distinct judgment nor any special difficulty to be overcome. Therefore it does not require a distinct habit, but only an extension or application of the same habit.

The antecedent is proved. It is plainly clear that the procedure comes from the same principles: if it applied other principles that did not belong to logic as teaching, then it would no longer be merely logic being used, but logic as teaching, since it would be handing down other principles; they would be distinct sciences proceeding from distinct principles, and so they would be called two teaching sciences, not one teaching and one being used. Therefore the use and direction of logic must necessarily agree in the principles of its teaching.

That it does not need a distinct facility and habit for the sake of application is clear from what was said in the preceding article: the entire difficulty of logic’s direction or ordering consists in knowing the second intentions themselves insofar as they are grounded in the first. Once this is known, the application itself presents no special difficulty, because application itself is made to things known through acts that, by their natural representation and tendency, regard objects, not through a moral or voluntary motion or an artful deduction. The whole art and ordering belongs to the ordered object’s side, through the second intentions, as was said. Therefore the difficulty is not in directing acts so that they may be elicited, but in knowing the objects to which the second intentions are applied.

Likewise, on the side of the objects themselves, once the rules and precepts of logic, which are taught demonstratively by its teaching part, are known, there is no difficulty in applying and using them in this or that subject matter; it requires only the addition of the subject matter, to which the rules apply and extend without any new difficulty to be overcome on their part. It is like someone who has the art of music or plays the lyre: from the same precepts of the art, that person can apply the fingers to any instrument offered. If the person cannot move the fingers, or cannot move them so readily, no new art is needed to overcome this difficulty, but bodily practice or something else to remove the impediment just mentioned. Thus the person who moves the fingers more readily does not acquire a new art but removes an impediment to its exercise. So when the intellect is exercised in syllogizing about different subject matters or sciences, it does not acquire a new art or habit distinct from the teaching of logic itself, but a more ready use of it.

OBJECTIONS ARE ANSWERED.

First it is argued to prove that logic being used is found only in the topical part, and not in the demonstrative part. For St. Thomas seems expressly to say in Metaphysics IV, lecture 4,¹⁴ that in the part of logic called demonstrative only teaching belongs to logic, while use belongs to physics and the other particular sciences; but the tentative and sophistical parts of logic have both teaching and use. Therefore, according to St. Thomas, the demonstrative part is not logic being used.

If it is said that St. Thomas is speaking of use in which one proceeds probabilistically from logical principles in the other sciences—which certainly belongs to the demonstrative part, as he teaches in Posterior Analytics I, lecture 20,¹⁵—and not of use in which logic provides the very syllogistic form and artful method to the other sciences, which also belongs to the demonstrative part.

The contrary is the case: the other sciences elicit their demonstrations through their own power, not through the power of logic, and produce them in an orderly way, otherwise they would not be demonstrations. But that second intention of syllogistic form, since it is something of reason, is not made; it results from the very cognition that demonstrates. Therefore neither the eliciting of a demonstration nor that method or form of reason requires logic’s eliciting activity and use.

THE REPLY is the solution given during the argument. And to the reply it is said that a demonstration proceeding from a particular science receives from that science the character of a special demonstration, from the special character of that science. But it receives the character of an ordered and artful procedure through logic’s direction, not through the particular science’s own power, insofar as logic influences the other sciences, whether through an effective influence impressing some reality in the acts or through direction from the side of the object, which it presents as ordered, as we now presuppose. Thus the particular science does both: it considers the special truth through its own power, and orders the object through the power of logic’s direction. Although that mode or syllogistic form is a being of reason resulting from cognition, it does not result from the cognition of that science insofar as it is a particular science, but from logic’s directive cognition, which directs all sciences universally and affects that particular science.

Second it is argued: The act of logic being used is neither scientific nor demonstrative; therefore it does not proceed from the habit of logic.

The consequent is clear: the habit of logic is evident and certain, since it is a science; therefore it cannot elicit an opinionative act, which is uncertain and nonevident. So the act proceeds from another habit, and thus the habit of logic as teaching differs from that of logic being used. Again, logic as teaching proceeds in a resolutive and speculative manner, while logic being used proceeds applicatively and compositionally; therefore they are different habits.

THE REPLY: The consequent is distinguished. That a probable act does not proceed from the habit of logic as its primary and per se act is granted; that it does not proceed from it secondarily and indirectly, or even by direction, is denied.

It is no problem for an evident and certain habit to elicit a probable act or even to direct one toward it as a secondary and imperfect act. There is less difficulty in the case of direction, because logic teaches by certain scientific rules how an opinionative assent should be directed. Consequently, although something is opinionative on the side of the matter, it is scientific on the side of the method of direction and the rules by which it proceeds. That the habit of logic itself elicits an opinionative act and does not merely direct it is more difficult, but can nevertheless be explained from what was said. In a scientific habit, the primary act, which proceeds perfectly and resolutely by deriving conclusions all the way to first principles, is always certain and evident. Yet there is no contradiction in its sometimes forming from the same principles an imperfect procedure that is not fully resolutive, but proceeds only disputatively and tentatively; such a procedure is probable. A generator produces not only a perfect effect perfectly like itself, for example, a human being or a horse, but sometimes also an imperfect one, such as an embryo or even a monster or something degenerating from its perfection, although the power is perfect; this occurs because of some impediment, the incapacity of the matter, or the agent’s failure to apply itself. Likewise, logical science can use reasoning and scientific principles without fully resolving, but by inquiry and trial; this is an imperfect act. St. Thomas also teaches in Summa theologiae II–II, q. 1, a. 4, that the habit of faith knows its own credibility evidently, and an opinionative habit knows probability, while each apprehends its object obscurely, namely, the thing believed or opined. Thus evidence and lack of evidence do not concern the same thing: one concerns the thing believed, the other its credibility.

Although these seem to be several acts specifically distinct, they are specifically distinct as it were materially, not formally or on the side of the formal rationale. A virtue can have diverse inadequate acts specifically distinct as it were materially and partially, as religion has prayer, devotion, and so forth, which are diverse inadequate and partial acts.

As confirmation, it is said that logic being used does not proceed compositionally on the side of the rules and principles it uses, since these are the very principles of logic as teaching; it only applies those rules to determinate subject matter so that speculation itself may be rightly ordered. The fact that the very method of speculation is applied to diverse subject matters does not give it the character of something practical, as we said above, because what is applied is speculation.

Finally it is argued: Prudence is a virtue and habit distinct from synesis and eubulia, as St. Thomas teaches in Summa theologiae II–II, q. 51, a. 2; yet they are distinguished only because these two judge and deliberate well, while prudence commands and carries out. Therefore, similarly in logic, the teaching and judging habit is distinct from the operating and using habit.

It is confirmed because repeated acts of logic being used generate some habit, but not the habit of logic as teaching, since they are not scientific acts and thus neither generate nor increase science; therefore they generate another habit, distinct from the teaching habit.

THE REPLY: The consequent is denied. The difference is that in prudence there is a distinct difficulty in commanding and applying the will to action, as compared with judging and deliberating; in logic there is not. The basis for this is taken from St. Thomas’s teaching in Summa theologiae II–II, q. 47, a. 8: the perfection of art consists in judging, not commanding, whereas the perfection of prudence is the reverse. Hence a craftsman who willingly errs in his craft is considered better than one who errs through ignorance; conversely, the one who willingly errs is more imprudent. This is especially true of the art of logic, whose matter is the acts of reason themselves: the entire difficulty for the intellect lies in judging or ordering some truth. Whatever remains, namely, directing other acts from this truth once known, presents no special difficulty, because the intellect naturally tends toward objects once they have been presented. Thus the entire art and ordering belongs to the side of objects, which are attained by cognition naturally tending toward them. In moral matters, however, after the good has been judged and known, the chief difficulty remains in applying the will because of its freedom, indifference, or resistance to the regulated good. Hence a distinct habit is required, in which prudence is perfected.

To the confirmation the reply is that acts of logic being used generate a certain facility by way of disposition and readiness in applying subject matter, not by way of a new art or habit. For a habit is newly generated or increased not by just any acts, but by those that per se attain the habit’s own specific rationale and formal motive, not those that follow secondarily or are merely disposed toward it. A habit is newly generated or increased only according to its substantial and formal rationale; other formalities are accessory.

An example is found in St. Thomas, Summa theologiae II–II, q. 144, a. 1, ad 5, where he says that repeated acts of modesty do not generate a habit distinct from temperance, because modesty is not a habit of perfect virtue but a disposition toward generating temperance. Therefore not all repeated acts, even imperfect and secondary ones, generate a new perfect habit such as science; they generate something imperfect in the genus of habit, which is as it were a disposition or a certain readiness in the very exercise of the art. The distinction between disposition or readiness and habit is better understood in things pertaining to the intellect, because sometimes we find a habit without ease in exercising it—for example, a habit of science that does not yet have ordered and ready species for all the other conclusions of the science. Conversely, we find ease in exercising without a habit in someone who has ordered species and frequent practice of all the conclusions, but who lost the habit through an error in some principle—for example, through an error in faith, someone lost the principles of true theology and consequently the habit of theology itself, but not the ordered species of its conclusions.