Perceptual Experience and Empirical Rationality

1. Perception is the capacity for knowledge through impacts of reality on the senses. At least since Aristotle, human beings have been singled out as a kind of living beings differentiated from others by rationality. In human beings, knowledge, including the knowledge yielded by perception, is rationality at work. As Sellars says, identifying something as a case of knowledge—and he means human knowledge—is placing an episode or state in the space of reasons, which he explains as the space of justifying and being able to justify what one says. I will say something at the end about how an account of human knowledge on these lines relates to what we might understand perception to be in non-human animals, which are not in the space of making and justifying claims. Perceptual experience, in the sense of experience in which the subject is perceiving, as opposed to merely seeming to be perceiving, affords human beings the grounds for the judgments that are the units of their perceptual knowledge: judgments that are knowledgeable by virtue of being non-defective acts of the capacity for knowledge that perception is. In an experience in which someone is perceiving, ways things are in the world are perceptually manifest to her. There is an obvious rationality in judging that things are some way if the judging subject can ground her judgment on an experience in which it is manifest to her that things are that way. And for a judgment to be perceptually knowledgeable just is for it to have that kind of rationality. To say that a judgment is grounded on an experience in which the subject perceives that things are as she judges them to be is just another way of saying the judgment is a non-defective act of the capacity for knowledge that perception is. One can be perceiving that things are some way only if things are that way. If a judgment that things are some way is grounded on an experience in which the subject perceives that things are that way, it conforms to a necessary and sufficient condition for being knowledgeable: the judgment’s being grounded as it is entails that things are as they are judged to be. Philosophers often think we should not put such a condition on perceptual knowledge; I will come back to this.