if the connection between cause and effect turns out to be only statistically valid and only relatively true, then the causal principle is only of relative use for explaining natural processes and therefore presupposes the existence of one or more other factors
Jung establishes the philosophical necessity of the acausal principle by demonstrating that the statistical character of natural law relativizes causality and compels the postulation of a complementary, non-causal mode of connection.
, The Structure and Dynamics of the Psyche, 1960thesis