Lecture 1 — Aristotle's Preface. Various previous opinions on the difference between generation and alteration.

Our next task is to study coming-to-be and passing-away. We are to distinguish the causes, and to state the definitions, of these processes considered in general—as changes predicable uniformly of all the things that come-to-be and pass-away by nature.

Further, we are to study growth and alteration. We must inquire what each of them is;

and whether alteration is to be identified with coming-to-be, or whether to these different names there correspond two separate processes with distinct natures.

On this question, indeed, the early philosophers are divided. Some of them assert that the so-called 'unqualified coming-to-be' is 'alteration', while others maintain that 'alteration' and coming-to-be are distinct.

For those who say that the universe is one something (i.e. those who generate all things out of one thing) are bound to assert that coming-to-be is 'alteration', and that whatever 'comes-to-be' in the proper sense of the term is 'being altered'.

But those who make the matter of things more than one must distinguish coming-to-be from 'alteration'. To this latter class belong Empedocles, Anaxagoras, and Leucippus.

And yet Anaxagoras himself failed to understand his own utterance. He says, at all events, that coming-to-be and passing-away are the same as 'being altered':' yet, in common with other thinkers, he affirms that the elements are many.

Thus Empedocles holds that the corporeal elements are four, while all the elements—including those which initiate movement—are six in number; whereas Anaxagoras agrees with Leucippus and Democritus that the elements are infinite.

Anaxagoras posits as elements the 'homoeomeries', viz. bone, flesh, marrow, and everything else which is such that part and whole are the same in name and nature. while Democritus and Leucippus say that there are indivisible bodies, infinite both in number and in the varieties of their shapes, of which everything else is composed—the compounds differing one from another according to the shapes, 'positions', and 'groupings' of their constituents.)

For the views of the school of Anaxagoras seem diametrically opposed to those of the followers of Empedocles. Empedocles says that Fire, Water, Air, and Earth are four elements, and are thus 'simple' rather than flesh, bone, and bodies which, like these, are 'homoeomeries'. But the followers of Anaxagoras regard the 'homoeomeries' as 'simple' and elements, whilst they affirm that Earth, Fire, Water, and Air are composite; for each of these is (according to them) a 'common seminary' of all the 'homoeomeries'.

3. In this book, therefore, the Philosopher first prefaces an introduction, in which he states his intention;

second, he carries it out, at on this question (314a6; [4]).

In the introduction he does three things.

First (314a1), he states what his main intention is. And this is in continuation with the end of the book On the Heavens, where he had said: we have now finished our examination of the heavy and the light. He now adds: our next task is to study coming-to-be and passing-away. Of all the things that come-to-be and pass-away by nature, i.e., of things that are naturally generated and corrupted, we are to distinguish the causes of these processes considered in general, assigning, namely, one set of causes for generation and another set for corruption, or else distinguishing the common causes by assigning them to the particular species of naturally generated and corrupted things, and state their definitions, i.e., either the definitions of generation and corruption or also of the things that are naturally generated and corrupted—for one must know the definitions of each, since natural science not only considers motions but mobile things themselves. He says, of things that come-to-be and pass-away by nature, because the study of the generation and corruption of artificial things does not pertain to natural science.

Second, when he says further, we are to study (314a3), he promises to reach conclusions on the other subsequent motions, namely, on alteration and growth, as to the nature of both.

Third, at and whether alteration (314a4), he promises to settle the matter of the comparison of the aforesaid to each other, namely, whether one should consider (or accept) the nature and notion of alteration and generation as being the same, or separate, i.e., distinct, so as to differ in notion and nature, as they are determinate, i.e., distinct, as to name.

4. Then, at on this question (314a6), he pursues his proposition.

First, he determines concerning generation and corruption in common and also concerning the consequent motions;

second, he determines concerning the generation and corruption of the elements, and he does this in book 2, at we have explained (328b26; [FIX]).

The first part is divided in two:

in the first he determines concerning generation and corruption in common and concerning the other consequent motions;

in the second he determines concerning certain things required for these, at we must first investigate (322b1; [FIX, L. 18]).

As to the first he does two things:

First, he inquires whether generation differs from alteration. This was the third of the things brought forward; nevertheless it must be discussed first, because, since it is the difference that determines a species, the appropriate notion of generation and corruption could not be known, if this remained unknown.

Second, he determines concerning generation and consequent motions, at we have therefore to discuss (315a26; [18]).

As to the first he does three things:

first, he cites various opinions of the ancients regarding the difference between generation and corruption;

second, he gives a reason for these variances, at and yet Anaxagoras (314a13; [7]);

third, he elucidates this reason at for the views of the school (314a24; [10]).

He says therefore first that some of the early philosophers said that what is called "simple," i.e., absolute, generation is the same as alteration, while others said that the two differ.

5. Then, at for those who say (314a8), he assigns the reason for the aforesaid diversity. Concerning this he does three things.

First, he explains why some identified simple generation and alteration. For there were some who posited there to be one material principle of all things—e.g., water, or air, or fire, or vapor. At the same time they held that the matter of a thing is its entire substance. From this it follows that the substance of a thing always persists. Hence generation does not in reality differ from alteration. In the words of Aristotle: all who say that everything, i.e., the universe, is one with respect to material substance, and who generate all things, i.e., cause all things, from one material principle—all such must say that generation is the same as alteration and that it is the same thing for something to be made principally, i.e., absolutely, and to be altered.

6. Second, at but those who make (314a11), he tells why others postulated that generation differs from alteration. For there were certain philosophers who posited several material principles, from the association and disassociation of which all things were said to come to be and to be destroyed. In this doctrine, association was called "generation," and disassociation "corruption." But alteration, they declared, came about in terms of any change affecting the parts. Thus Aristotle says: all who posited more material principles than one, as did Empedocles, Anaxagoras, Leucippus and Democritus—to all such it seemed that generation was one thing and alteration another.

7. Third, at and yet Anaxagoras (314a13), he makes an exception for Anaxagoras, who, Aristotle says, forgot his own words, as does a person who says things contrary to his own position. For although Anaxagoras, as the others, posited many elements, yet he singly declared that to be generated and corrupted is the same as to be altered. The reason for this difference is that, as is said in Physics I, Anaxagoras taught that things come to be by being abstracted from the compound. However, he placed not only elements but also accidents in the mixture. Consequently, he assigned the same manner of production to bodies, which come about through generation and corruption, as to accidents, which pertain to alteration—so that, just as flesh comes to be by being abstracted [from that mixture] so too whiteness. According to this, therefore, generation is no different than alteration.

8. Then, at thus Empedocles holds (314a16), he explains the above-mentioned reasoning.

First, by showing how some thinkers came to posit more than one principle; for in the case of those who posited but one, there was just one absolute way for things to come about.

Second, he explains why those who posited one principle denied a difference between generation and alteration, a difference which the others admitted, at those, then, who construct (314a29; [11]).

Regarding the first he shows wherein those who posited many principles differed.

First, he shows how Empedocles differed from all the others. And he says that the reason why we previously stated that the aforesaid philosophers posited several matters is that Empedocles posited the four elements as material principles, namely, earth, water, air and fire. These four, together with their movers, namely, friendship which combined, and strife which separated, he says to be in number 6. Consequently, he posited finite principles. But Anaxagoras and Democritus and Leucippus posited infinite principles.

9. Second, at Anaxagoras posits (314a18), he shows how Anaxagoras differed from Democritus and Leucippus. For Anaxagoras posited "homoeomerous" bodies, i.e., bodies with similar parts, to be the material principles—for example, infinite parts of flesh and of bone and of marrow and of other such, each part of which is "synonymous" with the whole, i.e., agreeing with the whole in name and notion. This theory has been explained in greater detail by Aristotle in Physics I.

But Democritus and Leucippus held that all sensible bodies are composed of certain indivisible bodies supposed to be infinite in multitude and "form," i.e., shape, for they said some were circular, some square, some pyramidic, and so on. But contrary to what Anaxagoras posited, they posited all these to be indifferent in nature and species. Yet, while these principles are indifferent in nature and species, nevertheless sensible bodies differ from one another depending on the different things out of which they are composed. However, this is not according to a difference in the species of nature, but in position and order—namely, as these are variously disposed in different bodies according to prior and posterior, before and behind, above and below, right and left.

10. Third, at** for the views of the school** (314a24), he shows how Anaxagoras differed from Empedocles, and he says that they seem to contradict one another. For Empedocles declared that fire, earth, air and water are the four elements, and that they are more simple than flesh and bone and such "homoeomerous" bodies, i.e., bodies of similar parts. The reason was that he posited that things come into being from the elements being assembled; hence those bodies that were assembled to form other bodies he called "elements."

Anaxagoras, on the other hand, posited bone and flesh and similar bodies to be the more simple, and the elements, namely, earth, water, air and fire, to be composite. His reason was that he held things to come to be through being separated from a mixture. Hence, since he saw that all other bodies are generated from air, water, earth and fire, he believed that there was in these four bodies a maximum mixture, so that all other bodies could be extracted from them. Thus he [Aristotle] adds that he called these four bodies "panspermia," i.e., the universal seeds of all other bodies, in the sense that these four were a mixture of the seeds of all other bodies.