substance

   Aristotle defined 'a substance' in his Categories as 'what is neither in a subject nor said of a subject', but in his Metaphysics as 'a determinate individual that is capable of existing on its own', that is, independently. Aristotle distinguishes two sorts of substance: primary substances (particular individuals, such as Socrates) and secondary substances (species and genera, such as the species of humanity). Many Christian philosophers have insisted that God is, strictly speaking, the only substance, since he is the only thing capable of existing on his own; everything else depends on him for its existence. But when the Nicene Creed describes the Son as being of one substance with the Father, it is not clear whether the framers of the creed had primary or secondary substances in mind, although they do seem to have had one of Aristotle's definitions in mind. That is, it is not clear whether they are saying that the members of the Trinity somehow compose a single particular individual (God) or whether they all share in a single genus (deity). Even if God is the only substance in a strict sense of 'substance', there may well be other substances in a looser sense; Descartes regarded matter as a single substance; Locke regarded individual material things as separate substances 'standing under' their properties. Locke could say nothing, however, about the substance or 'I-know-not-what' itself underlying all the properties, which problem has led some philosophers, such as Hume, to reject the concept of substance altogether, in favour of a theory that all that exists are just bundles of properties not inhering in anything. Those that believe in both mental and physical substances are faced with the additional problem of explaining how they interact. Whitehead thought that concentration on the concept of substance had led philosophy astray and instead proposed that philosophers should concentrate on the concept of a process; Whitehead's system of thought was termed process philosophy.

   See Descartes, René; Hume, David; Locke, John; metaphysics; ontology; philosophy, process; Whitehead, Alfred North

   Further reading: Hoffman and Rosenkrantz 1994 and 1997; van Inwagen 1990; Wiggins 2001; Woolhouse 1993