materialism is not a ‘fact’ but rather an hypothesis, and a metaphysical one at that – an hypothesis which is no more self-evidently true than the notion that the world is constituted by spirit. ‘Matter is an hypothesis’, Jung insists.
Clarke reports Jung’s central epistemological argument: materialism is a disguised metaphysics, not a scientific fact, and possesses no privileged truth-status over idealist alternatives.
, Jung and Eastern Thought: A Dialogue with the Orient, 1994thesis