When we look out across a field, how do we know one distant object is bigger than another, or that one is behind another? Why do we see everything in three dimensions, in proper relation to each other, instead of seeing everything “flat?”

The fact is that when we “see” things, we see them not only with our eyes, but with our minds as well. We see things in the light of experience. Our mind, based on certain experiences, helps us interpret what we see. And unless the mind can use the cues it has learned to interpret what we see, we can become very confused indeed.