LESSON 2

The Supreme Science of Truth, and Knowledge of Ultimate Causes

Chapters 1 & 2: 993b 19-994b 11

             151. It is only right to call philosophy the science of truth. For the end of theoretical knowledge is truth, whereas that of practical knowledge is action; for even when practical men investigate the way in which something exists, they do not consider it in itself but in relation to some particular thing and to the present moment. But we know a truth only by knowing its cause. Now anything which is the basis of a univocal predication about other things has that attribute in the highest degree. Thus fire is hottest and is actually the cause of heat in other things. Therefore that is also true in the highest degree which is the cause of all subsequent things being true. For this reason the principles of things that always exist must be true in the highest degree, because they are not sometimes true and sometimes not true. Nor is there any cause of their being, but they are the cause of the being of other things. Therefore insofar as each thing has being, to that extent it is true.

Chapter 2

             152. Further, it is evident that there is a [first] principle, and that the causes of existing things are not infinite either in series or in species. For it is impossible that one thing should come from something else as from matter in an infinite regress, for example, flesh from earth, earth from air, air from fire, and so on to infinity. Nor can the causes from which motion originates proceed to infinity, as though man were moved by the air, the air by the sun, the sun by strife, and so on to infinity. Again, neither can there be an infinite regress in the case of the reason for which something is done, as though walking were for the sake of health, health for the sake of happiness, and happiness for the sake of something else, so that one thing is always being done for the sake of something else. The same is true in the case of the quiddity.

COMMENTARY

             289. Having shown how man is  disposed for the study of truth, the  Philosopher now shows that the knowledge of truth belongs pre-eminently to  first philosophy. Regarding this he does two things. First (151:C 290), he shows that a knowledge of truth belongs pre-eminently to first philosophy. Second (152:C 299), he rejects a false doctrine that would render his proof untenable ("Further it is evident").

             In regard to the first he does two things. First, he shows that knowledge of the truth belongs to first philosophy. Second (151:C 290), that it belongs in the highest degree to this science ("But we know a truth").

             He proves these two propositions from two things established above in the prologue of this book, i.e., that wisdom is not a practical but a speculative science (27:C 53), and that it knows first causes (23:C 48).

             290. He argues from the first of these to the first conclusion in this way. Theoretical, i.e., speculative, knowledge differs from practical knowledge by its end; for the end of speculative knowledge is truth, because it has knowledge of the truth as its objective. But the end of practical knowledge is action, because, even though "practical men," i.e., men of action, attempt to understand the truth as it belongs to certain things, they do not seek this as an ultimate end; for they do not consider the cause of truth in and for itself as an end but in relation to action, either by applying it to some definite individual, or to some definite time. Therefore, if we add to the above the fact that wisdom or first philosophy is not practical but speculative, it follows that first philosophy is most fittingly called the science of truth.

             291. But since there are many speculative sciences, which consider the truth, such as geometry and arithmetic, therefore it was necessary to show that first philosophy considers truth in the highest degree inasmuch as it has been shown above that it considers first causes (23:C 48). Hence he argues as follows. We have knowledge of truth only when we know a cause. This is apparent from the fact that the true things about which we have some knowledge have causes which are also true, because we cannot know what is true by knowing what is false, but only by knowing what is true. This is also the reason why demonstration, which causes science, begins with what is true, as is stated in Book I of the Posterior Analytics.

             292. Then he adds the following universal proposition. When a univocal predicate is applied to several things, in each case that which constitutes the reason for the predication about other things has that attribute in the fullest sense. Thus fire is the cause of heat in compounds. Therefore, since heat is predicated univocally both of fire and of compound bodies, it follows that fire is hottest.

             293. Now he says "univocal" because sometimes it happens that an effect does not become like its cause, so as to have the same specific nature, because of the excellence of that cause; for example, the sun is the cause of heat in these lower bodies, but the form which these lower bodies receive cannot be of the same specific nature as that possessed by the sun or any of the celestial bodies, since they do not have a common matter. This is why we do not say that the sun is hottest, as we say fire is, but that it is something superior to the hottest.

             294. Now the term truth is not proper to one class of beings only, but is applied universally to all beings. Therefore, since the cause of truth is one having the same name and intelligible structure as its effect, it follows that whatever causes subsequent things to be true is itself most true.

             295. From this he again concludes that the principles of things which always exist, i.e., the celestial bodies, must be most true. He does this for two reasons. First, they are not "sometimes true and sometimes not true," and therefore surpass the truth of things subject to generation and corruption, which sometimes exist and sometimes do not. Second, these principles have no cause but are the cause of the being of other things. And for this reason they surpass the celestial bodies in truth and in being; and even though the latter are incorruptible, they have a cause not only of their motion, as some men thought, but also of their being, as the Philosopher clearly states in this place.

             296. Now this is necessary, because everything that is composite in nature and participates in being must ultimately have as its causes those things which have existence by their very essence. But all corporeal things are actual beings insofar as they participate in certain forms. Therefore a separate substance which is a form by its very essence must be the principle of corporeal substance.

             297. If we add to this conclusion the fact that first philosophy considers first causes, it then follows, as was said above (151:C 291), that first philosophy considers those things which are most true. Consequently this science is pre-eminently the science of truth.

             298. From these conclusions he draws a corollary: since those things which cause the being of other things are true in the highest degree, it follows that each thing is true insofar as it is a being; for things which do not always have being in the same way do not always have truth in the same way, and those which have a cause of their being also have a cause of their truth. The reason for this is that a thing's being is the cause of any true judgment which the mind makes about a thing; for truth and falsity are not in things but in the mind, as will be said in Book VI (558:C 1230) of this work.

             299. Further, it is evident (152).

             He rejects a position that would render the above proof untenable; for this proof proceeded on the supposition that first philosophy considers first causes. But if there were an infinite regress in causes, this proof would be destroyed, for then there would be no first cause. So his aim here is to refute this position. Concerning this he does two things. First (152), he points out what he intends to prove. Second (153:C 301), he proceeds to do so ("For intermediate things").

             He says, first, that from what has been said it can clearly be shown that there is some [first] principle of the being and truth of things. He states that the causes of existing things are not infinite in number because we cannot proceed to infinity in a series of causes belonging to one and the same class, e.g., the class of efficient causes. Nor again are causes infinite in species, as though the classes of causes were infinite in number.

             300. Then he explains his statement about an infinite number of causes in a series. He does this, first, in regard to the class of material causes. For it is impossible to have an infinite series in the sense that one thing always comes from something else as its matter, e.g., that flesh comes from earth, earth from air, and air from fire, and that this does not terminate in some first entity but goes on to infinity. Second, he gives an example of this in the class of efficient cause. He says that it is impossible to have an infinite series in the class of cause which we define as the source of motion; e.g., when we say that a man is moved to put aside his clothing because the air becomes warm, the air having been heated in turn by the sun, the sun having been moved by something else, and so on to infinity. Third, he gives an example of this in the class of final causes. He says that it is also impossible to proceed to infinity in the case of "the reason for which" something is done, i.e., the final cause; for example, if we were to say that a journey or a walk is undertaken for the sake of health, health for the sake of happiness, happiness for the sake of something else, and so on to infinity. Finally, he mentions the formal cause. He says that it is also impossible to proceed to infinity in the case of the "quiddity," i.e., the formal cause, which the definition signifies. However, he omits examples because these are evident, and because it was shown in Book I of the Posterior Analytics that it is impossible to proceed to infinity in the matter of predication, as though animal were predicated quidditatively of man, living of animal, and so on to infinity.