The common notion of one event causing another naturally inclines us to think of the cause as earlier and the effect as later. It is, however, unclear why the causal order must in this way comply with the temporal order. The possibility of a cause succeeding its effect in time clearly opens up baffling problems, but none seem to render the idea self-contradictory, and it has been floated as a way of treating some of the phenomena of quantum mechanics. See also causation.