Chapter 4

The concept of form

802. It is clear from what we have said that matter is the act in which and through which bodies exist,(35) that is, the act through which and in which corporeal qualities subsist. Matter is what our thought first understands when we mentally conceive bodies.

803. This act cannot be realised, however, in isolation from all the corporeal qualities conceived as potentially present in it. What perfects it are the corporeal determined qualities which we call 'form'.

804. Some of these qualities are variable. If they are altogether necessary for us to be able to think of realised matter, they are called substantial form of body and as such they have a part to play in constituting the act through which body can be conceived as suitable for realisation. In this sense, we say that form, too, is substance. In other words, it comes to be part of substance.

805. But simply as variables, these corporeal qualities are called accidental forms because what is necessary to the subsistence of a body remains indeterminate. Nothing more is needed than the presence of one or other of these qualities.

806. However, while it is possible on the one hand to conceive of bodies furnished with all the substantial and accidental qualities necessary for their realisation, they can be realised in different sizes. The same size can even be repeated any number of times. We say, therefore, that the continuous or discrete quantity of matter is not determined by either the concept of matter or that of form, but by that of realisation, which depends upon the will of the Creator who realises bodies.

807. Matter, therefore, is the first reason for conceiving everything present in a body as subsistent. Consequently, matter is the first element to be called 'substance' and 'first subject'. It follows that matter is also the subject of the substantial form, as the substantial form is the subject of accidents. Finally, realisation has its explanation not in body, but in the creating cause; it is not the subject of body, but that which makes the subject subsist.

Notes

(35) The word 'act' expresses every entity. The nature of act is taken, in our case, from the nature of bodies to which it refers, and which we have described.