The psychology of sense perception has taught us that without the use of both eyes, without a binocular vision, there would be no awareness of the third dimension of space. The depth of human existence in the same sense depends on the fact that we are able to vary our modes of seeing, that we can alternate our views of reality. Rerum videre formas [to see the forms of things] is a no less important and indispensable task than rerum cognoscere causas [to know the causes of things].

Ernst Cassirer, Essay on Man