 The History of Philosophy. Broad wrote on a variety of scattered figures in the history of philosophy, e.g. Bacon, Butler, Berkeley, Newton, Leibniz and Kant. A notable work is Five Types of Ethical Theory that (alongside careful discussions of such philosophers as Spinoza and Hume) includes a pioneering study of Henry Sidgwick’s The Methods of Ethics (1874), written at a time when Sidgwick’s work had passed into nearly complete oblivion. Noteworthy here also are the two posthumously published book length studies on Leibniz and Kant, respectively. Both of these contain shrewd philosophical comment that are of general philosophical interest.