This book is about how we see and how we visualize. But it is equally about how we are easily misled by our everyday experiences of these faculties. Galileo is said to have proclaimed (Galilei, 1610/1983; quoted in Slezak, submitted), "dots if men had been born blind, philosophy would be more perfect, because it would lack many false assumptions that have been taken from the sense of sight." Many deep puzzles arise when we try to understand the nature of visual perception, visual imagery or visual thinking. As we try to formulate scientific questions about these human capacities we immediately find ourselves being entranced by the view from within. This view, which the linguist Kenneth Pike (Pike, 1967) has referred to as the emic perspective (as opposed to the external or etic perspective), is both essential and perilous. As scientists we cannot ignore the contents of our conscious experience because this is one of the principle ways of knowing what we see and what our thoughts are about. On the other hand, the contents of our conscious experience are also insidious because they lead us to believe that we can see directly into our own minds and observe the causes of our cognitive processes. Such traps are nothing new; psychology is used to being torn by the duality of mental life --- its subjective and its objective (causal) side. Since people first began to think about the nature of mental states, such as thinking, seeing and imagining, they have had to contend with the fact that knowing how these achievements appear to us on the inside often does us little good, and indeed often leads us in entirely the wrong direction, when we seek a scientific explanation. Of course we have the option of putting aside the quest for a scientific explanation and set our goal towards finding a satisfying description in terms that are consonant with how seeing and imagining appear to us. This might be called a phenomenological approach to understanding the workings of the mind or the everyday folk understanding of vision. There is nothing wrong with such a pursuit. Much popular psychology revels in it, as do a number of different schools of philosophical inquiry (e.g., ordinary language philosophy, phenomenological philosophy). Yet in the long term few of us would be satisfied with an analysis or a natural history of phenomenological regularities. One reason is that characterizing the systematic properties of how things seem to us does not allow us to connect with the natural sciences, to approach the goal of unifying psychology with biology, chemistry and physics. It does not help us to answer the how and why questions; How does vision work? Or, Why do things look the way they do? Or, What happens when we think visually? The problem with trying to understand vision and visual imagery is that on the one hand these phenomena are intimately familiar to us from the inside so it is difficult to objectify them, even though the processes involved are also too fast and too ephemeral to be observed introspectively. On the other hand, what we do observe is misleading because it is always the world as it appears to us that we see, not the real work that is being done by the mind in going from the proximal stimuli, generally optical patterns on the retina, to the familiar experience of seeing (or imagining) the world. The question, How do we see appears very nearly nonsensical: Why, we see by just looking, and the reason that things look as they do to us is that this is the way that they actually are. It is only by objectifying the phenomena, by "making them strange" that we can turn the question into puzzle that can be studied scientifically. One good way to turn the mysteries of vision and imagery into a puzzle is to ask what it would take for a computer to see or imagine. But this is not the only way and indeed this way is often itself laden with our preconceptions, as I will try to show throughout this book. The title of this book is meant to be ambiguous. It means both that seeing and visualizing are different from thinking (and from each other), and that our intuitive views about seeing and visualizing rest largely on a grand illusion. The message of this book is that seeing is different from thinking and to see is not, as it often seems to us, to create an inner replica of the world we are observing or thinking about or visualizing. But this is a long and not always an intuitively compelling story. In fact, its counterintuitive nature is one reason it may be worth telling. When things seem clearly a certain way it is often because we are subject to a general shared illusion. To stand outside this illusion requires a certain act of will and an open-minded and determined look at the evidence. Few people are equipped to do this, and I am not deluded enough to believe that I am the only one who can. But some things about vision and mental imagery are by now clear enough that only deeply ingrained prejudices keep them from being the received view. It is these facts, which seem to me (if not to others) to be totally persuasive, that I concern myself with in this book. If any of the claims appear radical it is not because they represent a leap into the dark caverns of speculative idealism, but only that some ways of looking at the world are just too comfortable and too hard to dismiss. Consequently what might be a straightforward story about how we see, becomes a long journey into the data and theory developed over the past 30 years, as well into the conceptual issues that surround them.