Of course there’s an enormous amount of knowledge but only a fraction of what we need to know, and it isn’t necessarily the key fraction and, alas, we don’t know what the key fraction is so… so we don’t know exactly what to look for. We just… it’s like going into a jungle, you may have got through an enormous amount of jungle and seen an immense amount of… of plants and animals and rivers but you may not have found what you’re looking for, and you don’t even know it’s… even… some people will say it isn’t there. I mean, even if it is there you don’t know how far away you are from getting it. So that's the sort of analogy you would have to make. It isn’t as if this… in fact, again, I've… I've put this in this book I’ve just written that an enormous amount is known about both the psychology of seeing, about what is known about the brains of humans and animals because you can now do scans on humans when they’re doing certain tasks, certain visual tasks and other tasks and so on. In spite of that, they almost never tell the students that we don’t understand how you see anything, which is bizarre in a way.