 One family of epistemological issues about perception arises when we concern ourselves with the psychological nature of the perceptual processes through which we acquire knowledge of external objects. According to direct realism, we can acquire such knowledge because we can directly perceive such objects. For example, when you see a tomato on the table, what you perceive is the tomato itself. According to indirect realism, we acquire knowledge of external objects by virtue of perceiving something else, namely appearances or sense-data. An indirect realist would say that, when you see and thus know that there is a tomato on the table, what you really see is not the tomato itself but a tomato-like sense-datum or some such entity.