We therefore shall speak as follows, first discussing the whole of generation. For, it is conformable to nature, having first considered such things as are common, to contemplate afterwards the peculiarities of any individual. For we say that one thing is generated from another, and a different thing from a different thing, when we speak either of things simple or of such as are composite. My meaning is this: a man may become a musician; something also which is not musical may become a musician. Or a man, who is not a musician may become a musical man. That which is simply generated, therefore I call man and that which is not musical. The simple which is generated I call that which is musical, but the composite of which there is a generation, and which is generated, I consider as subsisting when we say that a man who is not a musician becomes a musician. But of these, the one is not only said to have become this particular thing, but also to have been generated from this particular thing. As for instance, a musician from that which is not a musician. But the other is not predicated of all things, for a musician is not generated from a man, but a man becomes a musician. Of things, however, which are generated as we say that things simple are generated, one thing when in generation or becoming to be, remains, but the other does not remain. For man remains and is in becoming a musician. But that which is not musical, and that which is void of music, neither simply nor in a composite manner, remains. But these things being defined from everything which is generated, this may be concluded by anyone who directs his attention to it That it is necessary, as we have said, there should always be something which is the subject of generation. And this, though it is one in number, yet it is not one in form. For by one in form I mean the same thing as one in definition. For the essence of man, and of that which is void of music are not the same and the the one indeed remains, but the other does not remain. That which is not opposed remains. For man remains, but that which is musical, and to that which is void of music, do not remain. Nor does that which is composed from both remain as, for instance, an unmusical man. But that something should be generated from something and that something should not become this particular thing, each of these is rather predicated of things which do not remain, as for instance, that which is musical is said to be generated from that which is void of music, but not from man. Nevertheless, this is sometimes similarly asserted of things which remain. For we see that a statue is generated from brass, and not that the brass is generated a statue. Of that, however, which is opposed and does not remain, the predication is made in both wa, viz., this particular thing is said to be generated from that, and that particular thing is said to be generated this. A musician also is generated from that which is void of music and he who was void of music becomes a musician. Hence also the like takes place in the composite, for from an unmusical man, a man void of music is said to have become a musician. Since, however, the term generation is multifariously predicated and some things are said not to be generated simply, but to be generated this particular thing, but simply to be generated is the property of essences only. This being the case, in other things it is evident that there must necessarily be something which is the subject of generation, for quantity and quality, that which is a relative, when and where, become the subjects of a certain thing, because essence alone is predicated of no other subject, but all other things are predicated of essence. But that essences and such other things as have a simple subsistence, are generated from a certain subject, will become evident to him who considers this affair. For there is always something which is placed under these, from which the thing produced is generated, as for instance, plants and animals from seed. But things which are simply generated are generated partly by a mutation of figure, as a statue from brass, and partly by addition, as things which are increased. Some, too, are generated by ablation as mercury from a stone, but others by composition, as a house. Others again are generated by a change in quality as things which are varied according to their matter. But it is evident that all such particulars as are thus generated are generated from subjects. So that from what has been said, it is manifest that everything generated is always a composite. And there is something indeed which is generated, but there is also something which this thing becomes. And this which is generated is twofold, for it is either the subject or the opposite. I mean that what is void of music is opposed, but that man is the subject. I also call the privation of figure, form, or order, that which is opposed, but the brass, the stone or the gold, the subject. It is evident, therefore, if those things are the causes and principles of things subsisting from nature, from which primarily they derive their being, and are generated not from accident, but what each is said to be according to essence. It is evident, if this be the case, that everything is generated from subject and form. For, a musical man is composed, after a certain manner, from man and musician. For you dissolve reasons (definitions) into the reasons of them. It is evident, therefore, that things generated are generated from these. The subject, however, is one in number, but two in species for man and gold, and in short matter are numerable, for it is more this particular thing and that which is generated is not generated from it according to accident. But privation and contrariety are accidents. Form, however, is one principle, as for instance, order or music or someone of other things which are thus predicated. Hence, the principles may be said to be two, and they may also be said to be three. They are also partly contraries, as if someone should speak of that which is musical, and that which is void of music, or of the hot and the cold, or the harmonized, and that which is deprived of harmony. They are likewise, partly not contraries, for it is impossible for contraries to be passive to each other. This, however, is solved because the subject is different. For this is not contrary, so that principles after a manner are neither more than contraries, but two as I may say in number. Nor, again, are they entirely two, because their essence is different, but three, for the essence of man is different from the essence of that which is void of music. And also the essence of that which is void of figure is different from that of brass. What the number therefore is of the principles of natural things which are conversant with generation, and after what manner they are so many has been declared. It is also evident that it is necessary something should subsist as a subject to contraries, and that the contraries should be two. But that after a certain manner this is not necessary. For the other of the contraries will be sufficient by its absence and presence to the production of change. But the subject nature may be scientifically known according to analogy for as is the brass to the statue, or the wood to the bed, or matter and that which is deprived of form to anything else which possesses form before it receives form, so is this subject nature, to essence, to this particular individual thing, and to being. This, therefore, is one principle, though it is not one, nor being in such a manner as this particular individual thing. Another principle is form, and further still the contrary to this, privation. But with respect to these, how they are two and how they are more than two has been declared above. In the first place, therefore, it has been said that principles are contraries only, and in the next place that it is necessary something else should be admitted as a subject and that there should be three principles. But from what has been now said, it is evident what the difference of the contraries is, how the principles are related to each other, and what is their subject. It is not, however, yet manifest whether form or the subject is the essence of a thing. But that the principles are three, and how they are three, and what the mode is of their subsistence, is evident. Hence, how many principles there are and what they are, may be from these things surveyed.
