But observe, said Hume, that we never perceive causes, or laws; we perceive events; and sequences, and infer causation and necessity; a law is not an eternal and necessary decree to which events are subjected, but merely a mental summary and shorthand of our kaleidoscopic experience; we have no guarantee that the sequences hitherto observed will re—appear unaltered in future experience. “Law” is an observed custom in the sequence of events; but there is no “necessity” in custom.
