Metaphysics

​The causes and principles are in one sense different for different things, but in another sense, if one speaks generally and analogically, they are the same for all. For one might raise the question whether the principles and elements of substances and of relations are different or the same, and so similarly for each of the categories. But it is absurd if they are the same for all; for then relations and substances will consist of the same elements. What then will this be? For there is nothing common apart from substance and the other categories, and the element is prior to that of which it is an element; but surely neither is substance an element of relations, nor any of these of substance. Further, how is it possible for all things to have the same elements? For none of the elements can be the same as the compound of elements, e.g. B or A cannot be the same as BA. (Nor indeed is any of the intelligible things an element, such as being or unity; for these belong to each of the compound things too). Therefore none of them will be either a substance or a relation; but it must be so. Therefore, the elements of all things are not the same. — Or, as we say, in one sense they are, and in another sense they are not; e.g. perhaps of sensible bodies, as form is the hot, and in another way the cold is the privation, and matter is that which potentially is these first and in itself, and substances are both these and the things composed of them, of which these are the principles, or whatever becomes one out of hot and cold, such as flesh or bone; for that which comes to be must be different from those. Of these things, then, the elements and principles are the same (though different for different things), but we cannot say this of all things, except by analogy; just as if one were to say that the principles are three: form, privation, and matter. But each of these is different for each genus, e.g. in color they are white, black, and surface; or light, darkness, and air, and from these day and night come to be. And since not only the inherent causes are causes, but also of the external ones, e.g. the mover, it is clear that principle and element are different, though both are causes, and the principle is divided into these; and that which acts as mover or stabilizer is a certain principle and substance. So that while analogically the elements are three, the causes and principles are four; but different things have different ones, and the prime cause as mover is different for different things. Health, disease, body; the mover is the art of medicine. Form, disorder of a certain kind, bricks; the mover is the art of building. And since that which moves is, in natural things, man for man, and in things of thought, the form or its contrary, in one way there would be three causes, and in another way four. For the art of medicine is in a way health, and the art of building is the form of a house, and man begets man; and besides these there is that which, as the first of all things, moves all things.