This essay concerns Adorno's articulation of an idea of philosophy as it is developed through his considerations of philosophy's form or mode of presentation. It hereby attempts to illuminate some of what remains obscure about Adorno's understanding of a renewal of philosophy after Marx and the crisis of German Idealism. Various forms–from "anti-system" and "constellation" to "essay," "fragment," "encyclopaedia" and "dictionary"–are examined for what they contribute to an idea of philosophy. This focus distinguishes this essay from other studies of form in Adorno that have predominantly literary or musical concerns.