and other such universal propositions that do not admit of change.

Hence, in their view, the sciences fall into three divisions:

1. A science that is never stripped of matter, whether in the mind or in external reality; this is natural science (physics), whose subject-matter is body.

2. A science that is abstracted from matter in the mind, though not outside the mind; this is mathematics, such as discourse on measurable powers, magnitude, and number.

3. A science that is abstracted from matter both mentally and externally; this is the divine science (metaphysics), whose subject is absolute existence together with the concomitants that befall it insofar as it is existence—its division, for example, into necessary and contingent, substance and accident.

The Five Substances

They further divide substance into: (a) that which inheres, (b) that which is the receptacle, (c) that which is neither inhering nor receptacle but is connected to them in a governing fashion, and (d) that which is neither inhering, receptacle, nor thus connected.

The first is form;

the second is matter—hylē—which in their language means the receptacle;

the composite of the two is body;

the third is soul;

the fourth is intellect.

These, for them, are the five divisions of substance.

With respect to the categories, most of them reckon the first among substances. A group of their later authorities, however—such as Ibn Sīnā—refused to call it a substance. They maintained that substance is that which, when it exists, exists in no subject, that is, in no receptacle that it must inhere in. Such a definition applies only to that whose existence is other than its quiddity; the first kind does not meet this condition, and therefore is not a substance. In this they diverged from