  The conception of genuine scientific knowledge that Locke inherits and in some manner retains, scientia, has its roots in Aristotle, as set out at the beginning of Book I, §2 of the Posterior Analytics. For Aristotle, only necessary truths are the objects of scientific knowledge, and since scientific knowledge requires knowledge of causes, it also requires knowing that the fact is necessary by knowing its necessary relations to its causes. Among Aristotle’s manifold causes, the main one in question here is the formal cause—the nature or essence—as Aristotle indicates  elsewhere.[2]