The dissertation is a study of Karl Marx's reflections on philosophic method. In it, I argue that Marx’s early writings are best understood as contributions to a mid-19th-century effort, among German followers of Hegel, to develop a tenable naturalistic method for philosophy. Marx’s method undergoes a series of definite, well-reasoned changes during the period 1841-46, culminating in a methodological naturalism concerned to explain rival theories away as illusions given rise to by misleading appearances. I argue that Marx’s reasons for making these changes are more sophisticated than has previously been recognized. I reconstruct two overlooked arguments, in Marx, against rival methods for philosophy, both of which charge their targets with enjoining a kind of excessive doxastic conservatism. I also reconstruct Marx’s early and mature methods, showing how they shape the fine-grained argument structure of the Economic and Philosophic Manuscripts of 1844 and The German Ideology, respectively.