This volume gathers together for the first time the philosophical journal articles that appeared during Leibniz's lifetime under his name or which would have been easily attributed to him due to other identifying marks. Its primary aim is to convey a sense of the way in which Leibniz's philosophical views would have been available to the reading public of the time. The distinction between the papers that Leibniz published that are philosophical and those that are concerned with what was then called 'natural philosophy' is somewhat arbitrary. However, the present volume is a companion to Leibniz: Journal Articles on Natural Philosophy (OUP, 2023), and all the articles that are plausible candidates for the label 'philosophical' can be found in one or the other. Among the thirty articles included here are seminal pieces such as 'Meditations on Knowledge, Truth, and Ideas', 'On the Emendation of First Philosophy', 'On Nature Itself', and the 'New System' and its accompanying 'explanations', along with Leibniz's responses to criticisms of the 'New System' by Pierre Bayle, René-Joseph de Tournemine, and François Lamy. Readers will also encounter less familiar pieces from the early 1690s in which Leibniz engages with Simon Foucher and offers a series of critical discussions of Descartes and Cartesian philosophy. Finally, the collection contains three extended reviews of works by other philosophers: Wolf Heinrich von Lüttichau' Pansophia, Samuel Pufendorf's On The Duty of Man and Citizen, and the Earl of Shaftesbury's Characteristicks of Men, Manners, Opinions, Times. In Three Volumes.