If anybody says he can think about quantum physics without getting giddy, that only shows he has not understood the first thing about them.

The very nature of the quantum theory ... forces us to regard the space-time coordination and the claim of causality, the union of which characterizes the classical theories, as complementary but exclusive features of the description, symbolizing the idealization of observation and description, respectively.

Those who are not shocked when they first come across quantum theory cannot possibly have understood it.

It is wrong to think that the task of physics is to find out how Nature is. Physics concerns what we say about Nature.

Every great and deep difficulty bears in itself its own solution. It forces us to change our thinking in order to find it.

If quantum mechanics hasn't profoundly shocked you, you haven't understood it yet.