I want to get some basics: How do you define consciousness? The simplest way to define consciousness is as subjective experience. Another one-word definition is “awareness.” Thomas Nagel, the N.Y.U. philosopher, wrote a piece back in the ’70s called “What Is It Like to Be a Bat?” His idea is: If we can imagine it is like anything to be a bat, then a bat is conscious, because that means it has some sort of subjective experience. Why did he choose bats? Well, they’re very different than we are. Instead of using eyesight, they use echolocation. They bounce signals off of objects to move through space. We can vaguely imagine going through the world with echolocation. Whereas my toaster, I can’t do that. I don’t have a sense of what it’s like to be my toaster.