According to an influential tradition, perception is a passive process, determined entirely by the features of the external world. On the contrary, this chapter maintains that perception is problem solving by the analytic method, hence it is an active process. Since, in the analytic method, hypotheses are obtained by non-deductive inferences, this means that perception is based on inference. The chapter discusses the evidence for this view, and the objections against it. It also maintains that perception may involve data from several sense organs. In particular, vision is based on the fact that we form hypotheses about objects of the external world from stimuli on the retina and from movements of the eye, head or of the whole body, by means of deductive inferences.