The way I think of it is that the brain must explain what the body is doing. If you notice that you're slaving away for weeks to prepare for a demo and you're really stressed about it, and what you're going to do is show the project you're an expert in to a guy who has some knowledge of it and then do what he says - you have to invent a reason for why you're doing this. For me, "I'm doing it for money and to keep my job" completely satisfies. For someone who is above such base notions there most be something higher - Jobs is a genius saint of Design.