sub specie aeternitatis See SPINOZA. substance, as defined by Aristotle in the Categories, that which is neither predicable (‘sayable’) of anything nor present in anything as an aspect or property of it. The examples he gives are an individual man and an individual horse. We can predicate being a horse of something but not a horse; nor is a horse in something else. He also held that only substances can remain self-identical through change. All other things are accidents of substances and exist only as aspects, properties, or relations of substances, or kinds of substances, which Aristotle called secondary substances. An example of an accident would be the color of an individual man, and an example of a secondary substance would be his being a man. For Locke, a substance is that part of an individual thing in which its properties inhere. Since we can observe, indeed know, only a thing’s properties, its substance is unknowable. Locke’s sense is obviously rooted in Aristotle’s but the latter carries no skeptical implications. In fact, Locke’s sense is closer in meaning to what Aristotle calls matter, and would be better regarded as a synonym of ‘substratum’, as indeed it is by Locke. Substance may also be conceived as that which is capable of existing independently of anything else. This sense is also rooted in Aristotle’s, but, understood quite strictly, leads to Spinoza’s view that there can be only one substance, namely, the totality of reality or God. A fourth sense of ‘substance’ is the common, ordinary sense, ‘what a thing is made of’. This sense is related to Locke’s, but lacks the latter’s skeptical implications. It also corresponds to what Aristotle meant by matter, at least proximate matter, e.g., the bronze of a bronze statue (Aristotle analyzes individual things as composites of matter and form). This notion of matter, or stuff, has great philosophical importance, because it expresses an idea crucial to both our ordinary and our scientific understandings of the world. Philosophers such as Hume who deny the existence of substances hold that individual things are mere bundles of properties, namely, the properties ordinarily attributed to them, and usually hold that they are incapable of change; they are series of momentary events, rather than things enduring through time. See also BUNDLE THEORY, PROPERTY. P.Bu.