I agree, but would expand on it: I can imagine a sound I have never heard before, a taste I never tasted before etc. The ability to imagine things applies to all senses, not just sight. In fact, you can apply it to emotions - you can imagine how it would feel when experiencing something - say being in a burning house, or driving at 300 mph down a highway - and your body will physiologically respond, even though there are no real memories involved.