 The allegiance to this picture has its source in the view that all thinking intended to result in the discovery or establishment of truths is inferring. A child sees a word on a page, an adult sees a misprint, and an illiterate sees a black mark. Each has eyes in perfect working order. According to this view, the difference between seeing black marks, a word, or a misprint has to do with the reasoning we bring to what is perceptually given. And sense-data (or, we may add, perceptual experience) play the role of what is given prior to any thinking, and prior therefore to any exploitation of knowledge or beliefs previously acquired. A datum, as it is used here, is something that we reason from and does not have to be reasoned to.