Niels Bohr said this quote

You can recognize a small truth because its opposite is a falsehood. The opposite of a great truth is another truth.

~ Niels Bohr

Prediction is very difficult, especially about the future.

~ Niels Bohr

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

~ Niels Bohr

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.

~ Niels Bohr