CHAPTER I

THE DEFINITION OF THE SOUL

             HITHERTO we have spoken of what our predecessors handed down to us about the soul. But let us now re-open the enquiry from the beginning and endeavour to determine what the soul is and what is its most comprehensive definition.§ 211

             Now, we say that one of the kinds of things that are is substance. Of this, there is one element, matter, which of itself is no particular thing; another, the form or species according to which it is called 'this particular thing'; and a third, that which is from both of these. Matter is, indeed, potency, and the form, act; and this latter has two modes of being, one, like knowledge possessed, the other, like the act of knowing.§§ 212-16

             Bodies especially seem to be substances; and, among these, natural bodies, for these are the principles of the others. Of natural bodies, some possess vitality, others do not. We mean by 'possessing vitality', that a thing can nourish itself and grow and decay.§§ 217-19

             Therefore every natural body sharing in life will be a substance, and this substance will be in some way composite. Since, however, it is a body of such and such a nature, i.e. having vitality, the soul will not itself be the body. For the body is not one of the factors existing in the subject; rather, it is as the subject and the matter. It is necessary, then, that the soul be a substance in the sense of the specifying principle of a physical body potentially alive. Now, substance [in this sense] is act; it will therefore be the act of a body of this sort.§§ 220-6

             Now this can mean one of two things: one, as is the possession of knowledge; another, as is the act of knowing. It is plain that it is like knowledge possessed. For the soul remains in the body whether one is asleep or awake. Being awake is comparable to the act of knowing, sleep to possession without use. Now knowledge possessed is prior in the order of generation, in one and the same thing. The soul, therefore, is the primary act of a physical body capable of life.§§ 227-9

             Such a body will be organic. Parts of plants, indeed, are organs, though very elementary--the leaf is the covering of the pericarp and the pericarp of the fruit: roots, too, are like mouths, for both draw in nourishment.§§ 230-2

             If, then, there is anyone generalisation to be made for any and every soul, the soul will be the primary act of a physical bodily organism.§ 233

             Hence it is unnecessary to enquire whether the soul and body be one, any more than whether the wax and an impression made in it are one; or in general, the matter of anything whatever, and that of which it is the matter. For while one and being are predicated in many ways, that which is properly so is actuality.§ 234