If B follows A, when are justified in saying A caused B? And
having made the claim that A caused B, what exactly have we asserted?
Since Hume destroyed the causal base of empirical observation
and distinguished between causal expectation and cause, the problem
of cause has been a philosophical raw end in science. If we develop
a general theory of psychology embracing all, then this problem
must arise somewhere within it and be resolved by it.