Man is an amphibian who lives simultaneously in two worlds— the given and the home-made, the world of matter, life and consciousness and the world of symbols. In our thinking we make use of a great variety of symbol-systems— linguistic, mathematical, pictorial, musical, ritualistic. Without such symbol-systems we should have no art, no science, no law, no philosophy, not so much as the rudiments of civilization: in other words, we should be animals.