Catharine Trotter Cockburn is best known for her Defence of Mr. Locke’s Essay of Human Understanding (1702). However very little has been said about Trotter’s treatment of Locke’s metaphysical commitments therein. In this paper I give a brief description of the history of Trotter’s Defence. Thereafter I focus on two (of the many) objections to which Trotter responds on Locke’s behalf: 1) the objection that Locke has not proved the soul immortal, and 2) the objection that Locke’s view leads to the absurd consequence that our souls are in constant flux. I argue that Trotter offers a compelling response to both of these charges. This is not only because of what Trotter explicitly claims in the Defence, but also because the Defence invites and encourages the reader to return to Locke’s text. I then argue that in Trotter we find additional insights and clarifications once we move past the two objections I just mentioned, and on to the related topic of personal identity. In this short paper I am not be able to offer a full explication or evaluation of Trotter’s treatment of Locke’s metaphysical commitments. I am, however, able to show that this aspect of Trotter’s Defence warrants careful consideration and further study.