Einstein on his stubbornly purist way of thinking.

Only one thing was clear to Einstein from Besso's last letter – which was that he had absolutely not understood his friend's idea: 'Are you talking of the possibility that there are atoms with identical cores which are exclusively differentiated by the ordering of their electrons? ... However, it is more likely that I have understood absolutely nothing of your idea. In this case the only profitable approach is if you explain the idea to me as if to a young student who knows as yet absolutely nothing. In fact, I also am very ignorant. This comes from my aversion for semi-empirical theorising which is no doubt very useful in practical terms, but not at all productive for deeper insights. Thanks to this attitude I have become a sort of stubborn heretic in the eyes of my colleagues'. On the subject of his research, he is working on a 'well-structured and completely rational' theory, although his mathematical methods are not up to drawing testable conclusions from it.