Cockburn Catherine (Trotter) (1679–1749), English philosopher and playwright who made a significant contribution to the debates on ethical rationalism sparked by Clarke’s Boyle lectures (1704–05). The major theme of her writings is the nature of moral obligation. Cockburn displays a consistent, non-doctrinaire philosophical position, arguing that moral duty is to be rationally deduced from the ‘nature and fitness of things’ (Remarks, 1747) and is not founded primarily in externally imposed sanctions. Her writings, published anonymously, take the form of philosophical debates with others, including Samuel Rutherforth, William Warburton, Isaac Watts, Francis Hutcheson, and Lord Shaftesbury. Her best-known intervention in contemporary philosophical debate was her able defense of Locke’s Essay in 1702. S.H.