I can't help but be surprised that one man should attain eminence in two such widely differing fields as psychology and mathematics. And right now I'm perfectly convinced of your ability to pass yourself off as a physicist. I don't understand it. The smile was more amused, without being in the least patronizing, nor offensive.
Man lives in a world of ideas.
Any phenomenon is so complex that he cannot possibly grasp the whole of it. He abstracts certain characteristics of a given phenomenon as an idea, then represents that idea as a symbol, be it a word or a mathematical sign. Human reaction is almost entirely to symbols, and only negligibly to phenomenon. When we think, we let symbols operate on other symbols in certain, set fashions - rules of logic, or rules of mathematics. If the symbols have been abstracted so that they are structurally similar to the phenomena they stand for, and if the symbol operations are similar in structure and order to the operations of the phenomena in the real world, we think sanely.