 By combining these external constraints on our understanding of the epistemological innovations of the Roman Books with their philosophical context—Philo’s prior position of mitigated skepticism and the criticisms it faced—we can see, at least roughly, how Philo may have given flesh to the basic outline above. Taken together, these considerations suggest three constraints on the range of the knowledge that Philo accepted. They suggest, first, that Philo supplemented the externalist bones of his new definition of cognition with the internalist constraints on assent that the mitigated skeptics had already identified: assent to a Philonian cognitive impression would only be warranted when the representational “richness” guaranteed by its causal history (condition [b] above) was confirmed by meeting the additional perceptual and coherence conditions Carneades had identified for persuasive impressions. Secondly, that Philo took Philonian cognition to apply primarily to experiential knowledge, i.e., the kind that we ascribe to ourselves in virtue of perception and to experts with practical skills, or something like “ordinary knowledge”. And thirdly, that Philo accordingly did not assume that the results of philosophical inquiry would often, or even usually, or perhaps ever, amount to knowledge when subjected to rational criticism through argument on either side. (The evidence that might support these three claims is collected in Brittain 2001: ch. 3.)