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9.1 Traditional Views of Substances

There have been two (at least) extremal positions possible in philosophy with regard to any changeable enduring substance.

      One position is exemplified by Spinoza and Leibniz, who defined substance as `that whose nature requires its separate existence'. On this view, substances are self-sufficient beings which contain within themselves the complete source of all their changes. Leibniz has for example that all natural changes of his monads come from within, as `an external cause can have no influence upon its inner being.' 9.1   The difficulty then, as Kant realised, is that on this account `it is not necessary for [a substance's] existence that it stand in relation to other things'9.2. It is a puzzle, on this account, why substances even have positional relations that might enable the acting of one substance on another. The possibility of interactions of substances can only be regained by denying that substances are self-sufficient beings. I want to deny that substances are fully actual and determinate with respect to external interactions. I want to look for some closer relation between substances and `powers' or `propensities', in order that substances may endure through changes in some of their properties (their `accidents') produced by interactions with other substances.

If substances were self-sufficient, there is always the difficult question of how their powers for interacting are supposed to be related to their `underlying' nature.   It is not clear, furthermore, whether it is possible to properly conceive of any `naked substance' apart from all its powers.   Locke explicitly had no clear idea of the relation between a substance and its powers, and it is debateable   (see Ayers [1975]) whether he distinguished any power-less substance.       One view is that of Boscovich, Faraday and Harré, whereby a substance is at a single place at any given time, around which its powers are `fields of force'. All inertia still resides in the point substance, and around it the field of force extends away indefinitely. However, it is still not perfectly clear how these `point centres of mutual influence' are related to the extended fields.

      The second general position is the denial of `substance' altogether, and of any sense of continued identity, in favour of pure process. We then have a purely event or flux philosophy. Reasons for this repudiation have varied. Sometimes it has been the alleged unknowability of the real constitution of substances. At other times it has been a preference for `flux' or `creativity' as against the `Parmenidean influence' that is seen to pervade much of Western philosophy.     Hume and Whitehead are perhaps the two most prominent figures here. As well, between the wars this century an ontology of `events' became popular,   especially under the influence of a common interpretation of relativity theory and a positivistic approach to metaphysics.   Russell's The Analysis of Matter [1927] is a good presentation of this position, wherein events are fixed in space and time. Paradoxically, they become then like fixed substances, and the understanding of event as `change' often fades.

  After the Second World War Nicholas Rescher [1962] noted that there was a general reaction to such an extreme event-and-no-continuant ontology. Many writers now repudiate `events' in favour of substances and their relations.   In the reaction, however, a very uncritical idea of `substance' was taken over, practically identical with `material object'. This has the result that there could be no very precise understanding of either the fact or the dynamics of real change.

With some philosophers, nevertheless, the realisation of the inadequacy of the event ontology came more moderately, and arguments were found for an ontology in which there are both events and continuants. Events could now be properly construed as real changes, by reference to the changes of the continuants involved.     This was done as early as W.E. Johnson [1924], who was trying to counterbalance the middle Whitehead's Concept of Nature [1920]: it was Johnson who coined the term `continuant'. Without such a term, he remarks9.3, it would be impossible to distinguish the case of two events A, B, say, causing two later events C & D, respectively, from their causing D & C, respectively.   The necessity for substantial continuants was further supported by Reck [1958], who argued against an ontology of only events, and for a position closer to that of Johnson. However, neither Johnson nor Reck attacked the problem of giving a fully-fledged account of such continuants: they did not consider the problem, for example, of how a substance is related to its powers.

  The present inquiry will therefore have as one of its starting points a process theory of discrete events, and will proceed with the help of Leclerc [1972]. Since, as we saw in chapter 2, some notions of dispositions or propensities are required in any useful science or philosophy of nature   (see also Thompson [1988]), processes will be analysed on this basis. We are led to postulate a new notion of `propensity fields', to see whether such things can continuously endure through certain types of interactions, and then to see whether we can identify these propensity fields with the `substances' of classical philosophy.     I will use however Johnson's [1924] term `continuant' to avoid a number of unwanted associations from the history of the term `substance'.

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Prof Ian Thompson


Author: I.J. Thompson (except as stated)