 This first stage gives the Academic a procedure that allows for discrimination between impressions while preserving the Academic thesis that nothing can be known. The second stage of Clitomachus’ defense drew on Carneades’ criticisms of the Stoic unitary notion of assent as simply a matter of taking an impression (or its content) to be true. Carneades had argued that this fails to account for the complexity of our cognitive life: many of our actions are not the product of distinct acts of assent, but are rather unconscious, or habitual, like animal action; and we sometimes deliberately act without assent, for instance, when we follow unendorsed hypotheses or act in conditions of uncertainty (see Bett 1990). On the basis of considerations of this sort, Clitomachus argued that we should distinguish “assenting” to an impression, in the Stoic sense of taking it to be true, from “approving” an impression, in the sense of acting on it or accepting it as if it were true. (See Cicero Ac. 2.104.)