In this chapter I attempt to answer the question posed in the title from two standpoints, first historically and then in terms of contemporary options in the field, the various different theories that are currently under discussion.1 But before I begin, I would like to clear up a common misunderstanding: philosophy of technology is not closely related to philosophy of science. Science and technology share a similar type of rationality based on empirical observation and knowledge of natural causality, but technology is concerned with usefulness rather than truth. Where science seeks to know, technology seeks to control. However, this is by no means the whole story.