Metaphysics – Hume and Wittgenstein

Metaphysics as traditionally conceived is concerned with what has to be the case, and also (therefore) with what cannot be the case. An object cannot be in two different places at the same time; a cause must occur before its effect; a pain cannot be felt by more than one person; you cannot access other possible worlds; I must know what I’m thinking about.

Philosophers asserting such things have always faced the question, ‘How do you know?’ Hume’s scepticism as to whether good answers were forthcoming to (various instances of) that question characteristically led him to diagnose the propensity to make metaphysical claims – e.g. as a tendency to project our felt psychological impulses onto the world; or as he put it, the mind’s tendency to ‘spread itself on external objects’. Metaphysics, for Hume, should be replaced by psychology. Volumes of unreconstructed metaphysics may be consigned to the flames. Insofar as we are left with any unexceptionable necessity-claims, these can either be taken as dressed-up expressions of psychological impulse, or as harmless statements of the relations of ideas (what later got called ‘analytic statements’).

Wittgenstein, in both his earlier and later work, likewise rejected the pretensions of metaphysical philosophy. He too was diagnostic in his approach, at any rate in his later writings. To speak in very broad-brush terms, where Hume’s psychological diagnosis had invoked our tendency to project, Wittgenstein’s invoked our tendency to be in the grip of a picture; and where Hume talked of relations of ideas, Wittgenstein mentioned ‘grammar’, as when he wrote ‘Essence is expressed by grammar’.(Philosophical Investigations 371).

These broad similarities or analogies don’t of course mean that there aren’t crucial dissimilarities. Hume would often approach some claim of necessity by asking, ‘Can’t I imagine the opposite?’ – construing that question as a psychological one, an issue to be settled by going in for some introspection. But Wittgenstein writes: