But then, of course, one can peek through the fingers, which is not only pleasurable but a lesson in practical optics.

But, actually, an affordance is neither an objective property nor a subjective property; or it is both if you like. An affordance cuts across the dichotomy of subjective-objective and helps us to understand its inadequacy. It is equally a fact of the environment and a fact of behavior. It is both physical and psychical, yet neither. An affordance points both ways, to the environment and to the observer.

The human young must learn to perceive these affordances, in some degree at least, but the young of some animals do not have time to learn the ones that are crucial for survival.

The hypothesis that things have affordances, and that we perceive or learn to perceive them, is very promising, radical, but not yet elaborated.

What a thing is and what it means are not separate, the former being physical and the latter mental as we are accustomed to believe.

The heart of the problem is not so much how we see objects in depth, as how we see the constant layout of the world around us. Space, as such, empty space, is not visible, but surfaces are.

Hence it is that the shape of something is especially meaningful.

The meaning or value of a thing consists of what it affords.

A mechanical encounter or other energy-exchange may cause tissue damage.

The abstract analysis of the world by mathematics and physics rests on the concepts of space and time.