Publisher Summary This chapter explores the provisional nature of hypotheses, meaning that there is nothing permanent, nothing final, about any hypothesis. In view of the fact that a hypothesis is central to any scientific investigation, theoretical or experimental, it is necessary to study hypotheses in more detail. But without hypotheses, there is no meaning or purpose to scientific investigation. Another way of saying this is that the hypothesis impels scientific investigation. There is a seeming exception to the above statement—namely, investigations in the classificatory sciences, such as zoology and botany. The uses of hypotheses are widespread and their varieties are large. Hypothesizing is part of human thought experiencing in daily lives. But to produce a hypothesis of the stature of the laws of motion is an extraordinary event, even among great scientists.