  We have been explaining the idea of our having shared responses to stimulation. For the most part, Quine assumes that assent to an observation sentence simply is such a response. This assumption, however, cannot be quite correct. It may look for all the world as if there were a rabbit in front of me, even though there is not. If I have no reason to be suspicious I will be disposed to assent to “Rabbit?”; if I know about the deception, however, I will not be. So my disposition to assent does not, after all, depend solely on my sensory stimulations at the time. It depends also on my internal state, whether I know that in this case the rabbit-like appearance is misleading. The difficulty arises because “There’s a rabbit” is corrigible, a feature which, on most accounts, it shares with just about every sentence other than those about the speaker’s current experience. If a sentence is corrigible then there will be circumstances in which it is false, even though those circumstances produce stimulation patterns which would generally lead observers to assent to it. But then some observers may know that the circumstances are of this deceptive kind and not be disposed to assent, while others have no such knowledge and are disposed to assent. The moral of this is that assent, even to observation sentences, is not a mere response to stimulation; the responder’s internal state (having ancillary knowledge, or not) may also play a role.