David Hume is famously supposed to maintain that inferences to the unobserved drawn on the basis of prior experience are entirely lacking in epistemic merit. Hume will show that the demands of the rational causation model cannot be met and hence reason so understood cannot be causally implicated in the inference. Keep in mind that the nature of the psychological inference is uppermost in the discussion. Gottfried Wilhelm. Leibniz denied associative transactions the status of reason because experience is consistent with changes in the underlying powers, thus underdetermining the course of nature. The power necessarily implies the effect; and therefore is there is a just foundation for drawing a conclusion from the existence of one object to that of its usual attendant.