 John Locke’s Essay Concerning Human Understanding (1690) is another foundational text of the Enlightenment. A main source of its influence is the epistemological rigor that it displays, which is at least implicitly anti-metaphysical. Locke undertakes in this work to examine the human understanding in order to determine the limits of human knowledge; he thereby institutes a prominent pattern of Enlightenment epistemology. Locke finds the source of all our ideas, the ideas out of which human knowledge is constructed, in the senses and argues influentially against the rationalists’ doctrine of innate ideas. Locke’s sensationalism exerts great influence in the French Enlightenment, primarily through being taken up and radicalized by the philosophe, Abbé de Condillac. In the Treatise on Sensations (1754), Condillac attempts to explain how all human knowledge arises out of sense experience. Locke’s epistemology, as developed by Condillac and others, contributes greatly to the emerging science of psychology in the period.