To address different questions, we must process information in different ways. In important examples, those methods of processing prove to be mutually incompatible. Thus no one approach, however clever, can provide answers to all possible questions. To do full justice to reality, we must engage it from different perspectives. That is the philosophical principle of complementarity. It is a lesson in humility that quantum theory forces to our attention… Complementarity is both a feature of physical reality and a lesson in wisdom.


You have to view the world in different ways to do it justice, and the different ways can each be very rich, can each be internally consistent, can each have its own language and rules. But they may be mutually incompatible — and to do full justice to reality, you have to take both of them into account.