 The principal thesis of Althusser’s last philosophical writings is that there exists an “underground” or little recognized tradition in the history of philosophy. Variously labeled a “materialism of the encounter” or “aleatory materialism,” the method which he uses to articulate this philosophy is to simply comment upon works by philosophers who exemplify this current and to point out where, how, and to what extent they do so. In addition to Marx, the philosophers that he cites as being part of this underground tradition include Democritus, Epicurus, Lucretius, Machiavelli, Spinoza, Hobbes, Rousseau, Montesquieu, Heidegger, Wittgenstein, and Derrida. From these readings in the history of philosophy, Althusser aims to suggest that this tradition exists and that it is both philosophically fecund and viable. He also wishes to return to and bolster the thesis he first ventured in the late 1960s that there are really only two positions in philosophy: materialism and idealism. As he understood it, the two tendencies are always in a war of opposition with the one functioning to reinforce the status quo and the other to possibly overcome it.