For thousands of years, sleep was viewed as an inseparable part of the order of nature, testimony to nature's good sense or the wisdom of the gods. No one was bothered by the question Why do we sleep? Sleep was the condition that separated the activities of one day from those of the next, and apart from dreaming, nothing of importance was considered to occur during those hours of oblivion. Dreaming was perceived not as a part of sleep but rather as the result of external influences exerted on the sleeper. Sleep was what happened between "Good evening" and "Good morning," but no more than that