Lecture II

I should like at the same time to draw your attention to something of which we have already spoken, namely, what I said about sleep and fatigue. There is much talk today about the reason for people having to sleep and it is said to because they are tired—so that tiredness is considered the essential cause of sleep. This is what is said today. Now from the most ordinary experience in life everyone knows that any leisured person who comes to a lecture, out of politeness shall we say, will often fall asleep when the lecture has hardly begun even if he isn’t tired—so that we may all come to the conclusion that fatigue is not entirely the cause of sleep. On the contrary, we should be nearer the truth in saying, not that we go to sleep because we are tired, but that we feel tired because we want to sleep. This would be more correct.