TNH 1.3.04.03
You may want to object: ‘We can reason from our past conclusions or principles without having recourse to the impressions from which they first arose.’ This is true, but not a sound objection; for even if those impressions were entirely wiped from the memory, the belief they produced may still remain. All reasonings about causes and effects are originally derived from some impression; just as one’s confidence in a demonstration always comes from a comparison of ideas, though the confidence may continue after the comparison has been forgotten.