Well, I hope I've convinced you that there are some real puzzles in vision. And that the main one that forms much of the theme of the course is the discrepancy between the world that's out there and the world that we end up perceiving, that we end up seeing in terms of our subjective awareness of the world. So let me just summarize the main points that we've gone through in this topic. And first of all, it's the obvious point that is the bottom line for all of these demonstrations, that the significance of images, what we have on the retina, and how we see those images for behavior, for what we need to do in the world to respond directly in the physical reality that, of course, is out there, that's inherently uncertain. That relationship between images and reality is just uncertain by its nature. That's the inverse problem. And this means that the real world is, in some very real sense, unknowable by direct, logical operations that we could imagine being performed on retinal images. Machine vision. Physical devices can do this in a way by measuring physical reality. But our eyes, our visual systems, don't measure physical reality. And, in that, sense the real world is just unknowable. In some sense, we behave correctly, so we know it. But the question at the end is, how does vision succeed in a world that's basically hidden in terms of its physical properties? And that's what we're going to be talking about for most of the rest of the course.