Substance

2. Early-modern heretical concepts of substance

Modern European philosophy began with a proliferation of variant conceptions of substance in an extended attempt to replace the dominant Aristotelian metaphysics and science with a new authoritative system. Later scepticism about the notion of substance arose with the rejection of this dogmatic enterprise. The very multiplicity of conceptions of substance may suggest that substance-based metaphysics was arbitrary and confused. Yet the various directions taken all fall within an intelligible framework of argument. The crucially productive move was the expulsion of teleological explanations from science through a reversion to something like the ancient atomists’ conception of matter as a substance possessing mechanical properties sufficient to explain all physical phenomena (see Teleology). Materialists such as Thomas Hobbes (1651) concluded that matter or body, determinately modified, is all there is (see Hobbes, T. §3). The variety of sensible qualities by which we distinguish things is a mere ’diversity of seeming’ consequent on differences in structure and motion. The activity of substances is simply the motion of bodies in accordance with necessary laws. Sensation and thought are themselves species of motion. More popular than materialism, however, in that religious age, was René Descartes’ dualism (see Descartes 1641), which postulated incorporeal thinking substance in addition to extended substance (see Descartes §8). A respectable philosophical motive for dualism was that it by-passed the insoluble problem of explaining consciousness, including ’seeming’ itself, in mechanical terms.

This new physics might seem far from the theory of predication, but mechanists saw themselves as explaining the logical relation between substance and accidents: accidents are simply the various and changing sizes, shapes and motions of bodies, limits or determinations of extension rather than Suárez’s distinct real entities mysteriously inherent in a subject. Descartes (1644) took it that, analogously, particular modes of thought are determinations of thought in general, and that the formal idea of a subject of extension or thought refers to nothing over and above these attributes. The connection with predication also figured in the system of Spinoza (1677), whose monism constitutes not only a holistic, deterministic philosophy of nature, but also a logical model according to which the ultimate subject of predication is the universe as a whole, of which individuals are modes or aspects (see Spinoza, B. de §§2–3). Leibniz (1686 and 1714), too, in arguing for his anti-materialist monadism, associated two principles: the claim that our awareness of ourselves thinking gives us our only intelligible paradigm of variety within a unitary, active substance, and the logical principle that in every true proposition the predicate is conceptually contained in the subject (see Leibniz, G.W. §§4–5). Partly by means of the latter principle he attempted to explain the identity and diversity of immaterial substances in a non-spatial, non-material world, and his failure supplies an invaluable philosophical lesson. There is, as Aristotle supposed, a demonstrable tie between concrete substantial existence and existence in space.

Logical theory and philosophy of science were differently linked by John Locke (1689), who rejected all claims to know essences and so to understand the substance – accident relation. Substances, including matter and mind, are known to us only through a plurality of disparate observable qualities and powers, which we take to flow from some common cause. Hence we define the primitive noun-predicates which are the names of substances in terms which include a place-marker for that unknown essence: ‘When we speak of any sort of substance, we say it is a thing having such or such qualities, as body is a thing that is extended, figured, and capable of motion’ (1689, II. xxiii, 3). ‘Substance’ is just a name for the unknown. Modes, on the other hand, such as a triangle, democracy or a triumph are not mind-independent unknowns, but constructs reflecting human interests and containing nothing more than the features by which they are defined (see Locke, J. §§4–5). Locke was not denigrating the notion of substance, but attacking the pretensions of dogmatic theories. Scepticism was taken further by David Hume(1739–40), however, for whom the philosophical conception of substance was deconstructed as a product of deranged imagination (see Hume, D. §2). After Hume, Immanuel Kant attempted to reinstate the notion on a new basis, advancing the ‘transcendental’ argument that, for objective experience to be possible, it must be experience of a substance (that is, matter) undergoing change in accordance with law. The very ineluctability of the category, however, he took as proof that it does not correspond to anything in independent reality, but is generated by the interplay of sense and intellect, the forms of judgment and the forms of sensibility (see Kant, I. §§5, 6).