 Cook Wilson was thus led to distinguish, in some of his most intriguing descriptive analyses, a further ‘form of consciousness’, different from both knowledge and belief (or opinion), which he called ‘being under the impression that’ (SI, 109–113). A typical example being when one sees the back of Smith on the street and, ‘being under the impression that’ it is a friend, say Jones, one slaps him on the back, only to realize one’s mistake when he turns his head. The “essential feature” of this state of mind is, according to Cook Wilson, “the absence of any sense of uncertainty or doubt, the action being one which would not be done if we felt the slightest uncertainty” (SI, 110). Thus, one did not falsely judge that the man on the street was Jones, because there was no judgement at all: one was merely ‘under the impression that’ it was him. Maybe one had some evidence that it was Jones, but the point is that one acted on it without questioning the evidence: it was not used as evidence, there was no assessment out of which one may be said to prefer this possibility that other possibility, because no other possibility was entertained. In this state of mind, the possibility of error is somehow excluded, given that it does not occur to one that ‘This man is Jones’ might be false. It is thus not the case that one thought that one knew but really did not, because it is not true that to begin with one thought one knew, since one had not reflected on one’s evidence. The absence of doubt or uncertainty opens the door to the possibility of being mistaken while taking oneself as being certain.