LESSON 4

This Science Considers the Principles of Demonstration

  Chapter 4: 1061b 17-1061b 33

             932. And since the mathematician uses the common axioms in a particular way, it must be the office of first philosophy to study principles of this kind. For the axiom or principle that "when equals are subtracted from equals the remainders are equal" is common to all quantities. But mathematics, assuming [principles of this kind], makes a study of some part of the quantified as its proper subject matter, for example, lines or angles or number or some of the other kinds of quantity. Yet it does not consider them inasmuch as they are beings but inasmuch as each is continuous in one, two or three dimensions. Philosophy, however, does not investigate those things which are in some part of matter insofar as each has some attribute, but it considers each of these particular things from the standpoint of being insofar as it is being.

             933. Now what applies in the case of the science of mathematics is also true of the philosophy of nature; for the philosophy of nature studies the attributes and principles of beings inasmuch as they are moved, not inasmuch as they are beings. But, as we have said, the primary science considers these attributes and principles insofar as their subjects are beings, and not in any other respect. For this reason it is necessary to hold that this science and the science of mathematics are parts of wisdom (319-23; 900-01).

COMMENTARY

             2206. Having shown how the investigations of this science are concerned with beings and with the attributes which belong to being as being, the Philosopher now shows how the investigations of this science are concerned with the first principles of demonstration.

             This is divided into two parts. In the first (932:C 2206) he shows that it is the office of this science to consider these first principles of demonstration. In the second (934:C 2211) he draws his conclusions about one principle of demonstration which is prior to the others ("There is a principle").

             In regard to the first he does two things. First (932:C 2206), he clarifies his thesis by considering the science of mathematics; and second (933:C 2209), by considering the philosophy of nature ("Now what applies").

             In the first part he uses the following argument: all the common axioms which are used by the particular sciences in a way peculiar to themselves and not in their common aspect belong to the consideration of this science. But the first principles of demonstration are used by the science of mathematics and by other particular sciences in a way peculiar to themselves. Therefore an investigation of these principles insofar as they are common belongs to the science which considers being as being.

             2207. He accordingly says that, since the mathematician uses "the common axioms in a particular way," i.e., insofar as they are adapted to his subject matter, it must be the function of first philosophy to consider such principles in their common aspect. For these principles are taken as principles of the sciences insofar as they are adapted to some particular subject matter. He clarifies his statement by an example.

             2208. The principle that "when equals are subtracted from equals the remainders are equal" is common to all instances of quantity which admit of equality and inequality. But the science of mathematics presupposes principles of this kind in order to make a special study of that part of quantity which constitutes its proper subject matter; for there is no mathematical science which considers the attributes common to quantity as quantity, because this is the work of first philosophy. The mathematical sciences rather consider those attributes which belong to this or to that quantity; for example, arithmetic considers the attributes that belong to number, and geometry considers those that belong to continuous quantity. Thus the arithmetician uses the above-mentioned principle only inasmuch as it has to do with numbers, and the geometer uses it inasmuch as it has to do with lines and with angles. The geometer, however, does not consider this principle inasmuch as it relates to beings as beings but inasmuch as it relates to being as continuous, whether it is continuous in one dimension, as a line; or in two, as a surface; or in three, as a body. But first philosophy does not study the parts of being inasmuch as each has certain accidents; but when it studies each of these common attributes, it studies being as being.

             2209. Now what applies (933).

             Then he makes the same thing clear by considering the philosophy of nature. He says that what applies in the case of the science of mathematics is also true of the philosophy of nature; for while the philosophy of nature studies the attributes and principles of beings, it does not consider beings as beings but as mobile. The first science, on the other hand, deals with these inasmuch as they are being, and not in any other respect. Hence, the philosophy of nature and the science of mathematics must be parts of first philosophy, just as any particular science is said to be a part of a universal science.

             2210. The reason why common principles of this kind belong to the consideration of first philosophy is this: since all first self-evident propositions are those of which the predicate is included in the definition of the subject, then in order that propositions may be self-evident to all, it is necessary that their subjects and predicates should be known to all. Common notions of this type are those which are conceived by all men, as being and non-being, whole and part, equal and unequal, same and different, and so on. But these belong to the consideration of first philosophy; and therefore common propositions composed of such terms must belong chiefly to the consideration of first philosophy.