He espoused a principle of complementarity; there are mutually contradictory ways of looking at reality which together give us a deeper understanding.
He thought that science doesn’t describe reality as it is but our ways of conceptualizing it.
He rooted everything in concrete action and was an admirer of William James.
He also liked Lao Tzu and the Buddha.
His philosophy gave him the werewithall to see that the photon was both wave and particle — that is, it had empirical teeth.