EPISTEMOLOGY same thing as a belief: belief involves an extra item, namely assent; assent, unlike appearance, is a voluntary matter An appearance is cognitive if it is worthy of assent Cognition is between knowledge and belief in that, unlike belief, it is never false, and unlike knowledge, it does not involve the resolution never to change one’s mind.6 A cognitive appearance, we are told, is ‘that which arises from what is and is stamped and impressed exactly in accordance with what is’ (D.L 46; Cicero, Acad 77) Well and good: clearly such an impression (as we may call it) is worthy of assent A wise man will have no mere beliefs, Zeno said (Cicero, Acad 77); and no doubt this can be achieved if the wise man assents only to cognitive appearances But how I know whether an appearance is cognitive or not? Is it a matter of an appearance being so clear and distinct that it actually forces my assent, so that I cannot help but believe? Or does it have certain features that I can use as a criterion by which I decide to confer an assent that I might have withheld? Our evidence is not totally clear, but we are given some indications by the examples that survive First, we are told that the impressions of the insane are not cognitive (Sometimes, indeed, the Stoics denied that they were genuine impressions, calling them instead ‘phantasms’; D.L 49.) They ‘arise purely externally and fortuitously, so that they are often not positive about them and not assent to them’ (S.E., M 248) But suppose they assent to them: clearly that does not make them cognitive, since they are not true and only a true appearance can be cognitive But what epistemological rule have the insane violated? Well, perhaps they have not examined the degree of detail in their impression: for a second piece of information we are given is that a cognitive impression must be highly comprehensive, so that all the characteristics of its original are reproduced ‘Just as the seals on rings always stamp their features accurately on the wax, so those impressions that create cognition of objects should incorporate all their peculiarities’ (S.E., M 750) However, if cognitive impressions are ones that are fully comprehensive in detail, they must be very few and far between Perhaps, we might conjecture, cognitive impressions have a specially persuasive quality that marks them out The Stoics did indeed classify impressions in terms of their persuasiveness into four classes: So Frede, CHHP 296 V 171