  Cockburn responds to Burnet by showing that Locke’s epistemology can satisfy these concerns. Cockburn approaches the question of Locke’s epistemological foundations by emphasizing an aspect of Locke’s theory of ideas of which Locke himself makes little use in his account of moral knowledge. However, it is a concept that he uses in his proof of God’s existence (the proof of which Cockburn reiterates in her Defence). Cockburn’s moral theory employs Locke’s concept of reflection as a foundation not just for our knowledge of God, but also as a means for human moral knowledge. She argues that it is by reflecting upon the operations of our own minds that we can reach an understanding of both human and divine nature. According to Cockburn, morality is grounded in human nature, and the truth of moral laws is guaranteed by the fact that humans are designed by God. This emphasis on human nature leads Cockburn quite naturally into a fitness account of morality that predates Clarke’s own view – human nature entails that certain actions are fit and appropriate for humans and certain are not. In later works, Cockburn explicitly adopts the language of fitness relations to describe the necessary moral order arising from our created natures.