Well, I’ve been trying to classify them. Actually, that’s what I do in my old age, I’ve been trying to look at all the illusions I can find or discover or know about, and then I put them into classes and I think in biology it’s immensely important, you think of evolution and classifying species, I mean chemistry and all of that, periodic table, incredibly important for revealing the ultimately structure of atoms. Now, I think the same is true with illusions. I think classifying them is really important but to classify them you have to relate the things to some sort of theory to get the criterion for the classes so that the classification is not empty, it actually relates to the theory and can modify the theory. If a theory predicts that one phenomenon should be different from another or in some way similar, you know, in order words is will modify the classification, that’s the power of the theory but then the power of the classification is it can modify the theory and, of course, when you’ve got a classification and you’ve got a gap, you’ve got something missing, then you might say, oh, golly, there’s got to be something in that gap for the whole story to work, that then suggests either you look for more data or you look at the theory again. And so that interplay between phenomena and classifying them and then the theory, I think is what science is all about and I’m trying to do that with illusions. What about illusions in art? Well, art, of course, is amazingly interesting because you’re representing the world of three dimensional, solid objects with pigments which effectively are not solid on a flat screen and how do you compress the world of three dimensions into a flat screen? This, of course, is something that Leonardo thought about, I mean it goes back certainly 400 years in the history of art and I’m very, very interested in that. How the brain works when you cut the information from three to two dimensions but you’re representing three dimensions. What happens is you get ambiguity. In other words, you get many possibilities from the same pattern as to what the object might be and ambiguity is an important class of illusions. Now, what is interesting is that ambiguities can be dynamic. The brain will guess one thing, change its mind, and say, no, no, it’s not that, it’s another, and it’ll flip from one possibility to another spontaneously and you see the thing flipping. Turner actually used this sort of thing in a very subtle way in his paintings, which gave his paintings life. As you go on looking at them, there are subtle changes in the sky, in the clouds, because of this ambiguity generated by the observer but given by Turner’s painting which is deliberately vague and misty, indeterminate, so that the viewer’s brain can take off, be creative, and entertain various possibilities. That’s why Turner is such an amazing painter; he controlled the viewer’s brain, allowing it freedom to entertain alternative possibilities.