In this post, Susanna Siegel, Professor of Philosophy at Harvard University, introduces her book, The Rationality of Perception.
On a traditional conception of the human mind, reasoning can be rational or irrational, but perception cannot. Perception is simply a source of new information, and cannot be assessed for rationality. I argue that this conception is wrong. Drawing on examples involving racism, emotion, self-defense law, and scientific theories, The Rationality of Perception makes the case that perception itself can be rational or irrational.
The Rationality of Perception argues that reasoning and perception can be deeply intertwined. When unjustified beliefs, fears, desires, or prejudices influence what we perceive, we face a philosophical problem: is it reasonable to strengthen what one believes, fears, or suspects, on the basis of an experience that was generated, unbeknownst to the perceiver, by those very same beliefs, fears, or suspicions? I argue that it is not reasonable-even though it may seem that way to the perceiver. In these cases, a perceptual experience may itself be irrational, because it is brought about by irrational influences.
Here’s a simple example. Jill fears (without good reason) that Jack is angry with her. As a result of her fear, Jack’s face looks angry to her when she sees it. If you saw Jack, you’d see his neutral expression for what it is. There’s no need for Jill to jump to conclusions from what she sees. Her fear’s influence on perceptual experience makes it simpler for her: she can just believe her eyes.
Let’s suppose that Jill has no idea that her fear has influenced her perceptual experience. To her, she’s simply seeing Jack, and following common sense in believing her eyes - since as far as she can tell, she has no reason not to believe her eyes.
Is it reasonable for Jill to believe her eyes, when her visual experience is a projection from an unreasonable fear or presumption? It might seem that the answer is Yes. What else is Jill supposed to believe, given that she has no idea her fear has been projected onto her experience? In countless other situations, it’s reasonable to believe what you see. If you want to know whether there’s mustard in the fridge, for instance, then if you see some mustard (and have a visual experience of a sort that typically goes with seeing mustard), it’s clearly reasonable to believe that the fridge contains mustard.