 Another point of contestation has to do with the extent to which Locke thought natural law could, in fact, be known by reason. Both Strauss (1953) and Peter Laslett (Introduction to Locke’s Two Treatises), though very different in their interpretations of Locke generally, see Locke’s theory of natural law as filled with contradictions. In the Essay Concerning Human Understanding, Locke defends a theory of moral knowledge that negates the possibility of innate ideas (Essay Book 1) and claims that morality is capable of demonstration in the same way that Mathematics is (Essay 3.11.16, 4.3.18–20). Yet nowhere in any of his works does Locke make a full deduction of natural law from first premises. More than that, Locke at times seems to appeal to innate ideas in the Second Treatise (2.11), and in The Reasonableness of Christianity (Works 7:139) he admits that no one has ever worked out all of natural law from reason alone. Strauss infers from this that the contradictions exist to show the attentive reader that Locke does not really believe in natural law at all. Laslett, more conservatively, simply says that Locke the philosopher and Locke the political writer should be kept very separate.