An attempt to restate Marx's critical method in terms of Spinozist dogmatic epistemology was central to Louis Althusser's conception of Marxist philosophy. Although it is no longer necessary to argue that this ‘restatement’ had almost no ground in Marx's own thinking, it was a highly significant expression of the essence of dialectical materialism. Through discussion of Hegel's critique of Spinoza, it will be argued that a democratically acceptable method of criticism of the mistaken beliefs of others, such as Marx developed in Capital, must take a resolutely anti-dogmatic approach which has the principle of winning subjective conviction at its core.