Of Locke's major claims in the "Essay Concerning Human Understanding" and "Some Thoughts Concerning Education", two played a defining role in eighteenth-century educational theory. The first is that education makes the man; as Locke writes at the opening of his treatise, "I think I may say that of all the men we meet with, nine parts of ten are what they are, good or evil, useful or not, by their education." In making this claim, Locke was arguing against both the Augustinian view of man, which grounds its conception of humanity in original sin, and the Cartesian position, which holds that man innately knows basic logical propositions. In his "Essay" Locke posits an "empty" mind—a "tabula rasa"—that is "filled" by experience. In describing the mind in these terms, Locke was drawing on Plato's "Theatetus", which suggests that the mind is like a "wax tablet". Although Locke argued strenuously for the "tabula rasa" theory of mind, he nevertheless did believe in innate talents and interests. For example, he advises parents to watch their children carefully to discover their "aptitudes," and to nurture their children's own interests rather than force them to participate in activities which they dislike—"he, therefore, that is about children should well study their natures and aptitudes and see, by often trials, what turn they easily take and what becomes them, observe what their native stock is, how it may be improved, and what it is fit for."