35 On Whole
On Whole into its accidents, an accident into its substances or an accident into its accidents, the term 'accident' is used to mean that which is contingently predicated of something, viz., that actual existent which is designated by the subject. And it is clear that frequently in the authorities 'accident' is not used for some accidental thing really inhering in substance, but for 'what can be contingently predicated of substance'. If the aforesaid author had taken 'accident' for something really inhering in a subject, he should have said that man is divided into whiteness and blackness and not into white men and black men and, similarly, in the other cases.
35: On Whole The word 'whole' has a numberofsenses. In one sense we say that a whole is something incorporating many parts without which it cannot exist in nature.
It is impossible that a man exists without his body and rational soul, that air exists without the relevant matter and form, and that wood exists without this or that part. In all these cases the part belongs to the essence of the whole and not vice versa.
In another sense we call something a whole which is common to many. In this sense a genus is a whole with respect to its species, and a species is said to be a whole with respect to its individuals. Here, a whole is something common.
It is in this sense that logicians frequently use the term.
But for every sense of the term 'whole' there is a corresponding sense of the term 'part'. Thus, some parts belong to the essence of the whole while others are said to be parts only because they are less general than that of which they are said to be parts. Finally, we call those things subjective parts which belong to the essence of the whole no more than the whole belongs to their essence; and as that kind of part can exist without its whole, so also can the corresponding whole exist without its parts.
Although the words 'part' and 'whole' have a number of other senses, these will suffice for the present.