  Although primarily concerned with moral issues, Cockburn philosophical writings (which are taken here to include The Defence of Mr. Locke’s Essay of Human Understanding (hereafter referred to as the Defence), Remarks upon some Writers and Remarks upon the Principles and Reasonings of Dr. Rutherforth’s Essay) address a range of philosophical issues. In the Defence, she answers Burnet on a series of issues regarding the deficiencies of Locke’s empiricism, which include not only moral knowledge, but also the knowledge humans can have of God’s veracity and of the immortality of the human soul. There is also a broad range of topics addressed in her work Remarks upon some Writers, in which Cockburn begins by addressing several philosophical issues – necessity, the infinitude of space, and the nature and existence of spirits with regard to the notion of substance.  The latter discussion revolves generally around epistemological concerns regarding the knowledge of real essences and the nature of substance, in which she argues that spirits must have extension of a sort in order to be proper substances. She makes this argument by appeal to a broadly Lockean view regarding substance.