Imagine that you are a piece of iron. So there you are, sitting around doing nothing, as usual, when along comes a drop of water. What will be your perception of the water? Yes, I know, a bar of iron doesn’t have a brain, and it wouldn’t have any perception at all. But let’s ignore the inconvenient facts and imagine what it would be like if a bar of iron could perceive the water.

From the standpoint of a piece of iron, water is above all /rustish/. Now return to your perspective as a human. You know that rustishness is not really a property of water itself but of how it reacts with iron.

The same is true of human perception. For example, you see grass as green. But green is no more a property of grass than rustish is a property of water. Green is the experience you have when the light bouncing off grass reacts with the neurons in your brain. Greenness is in us - just as rust is in the piece of iron.