SOURCES OF SCEPTICISM IN ATOMIC THEORY

Abstract

I WANT to distinguish two types of assertions, doubts, denials, concerning the existence of atoms and other like entities. One type I shall call the scientific assertion, doubt, etc., or more generally doubt on the phenomenological level (0-level).1 The other I shall call an epistemological assertion, doubt, etc. (e-level). To take s-level discourse first. At this level, it will make straightforward sense to say such things as that, whilst originally we had very little evidence for the atomicity of matter, later discoveries greatly strengthened our belief in the physical reality of atoms. Or again, the following way of talking will be in order: Whilst originally the assumption of chemical atoms seemed plausible, subsequent discoveries threw considerable doubt on this. (I shall in a moment discuss this case in detail.) Even this will be perfectly in order: some features of the atoms of elementary kinetic theory are clearly contrary to physical possibility (e.g. zero-volume); to this extent they are abstractions or fictions. In all these cases strictly scientific considerations will determine the language of our choice, a language which operates within a conventional framework where expressions such as fiction, physical hypothesis, bare assumption, evidence for the existence of, and so on, have a relatively fixed grammar. Similarly, the usual distinctions between direct and indirect evidence will be made without causing any questions. Thus if we say that we have only indirect evidence for the existence of atoms, we shall of course mean that we have direct evidence for something else and that all this is a matter of degree; for instance, that we ' see directly' the instruments which give us information about these atoms.