Combine general relativity and quantum theory into a single theory that can claim to be the complete theory… — Lee Smolin

Many of the founders of quantum mechanics, including Einstein, Erwin Schrödinger, and Louis de Broglie... were realists. For them quantum theory... was not a complete theory, because it did not provide a picture of reality absent our interaction with it. On the other side were Niels Bohr, Werner Heisenberg, and many others. Rather than being appalled, they embraced this new way of doing science.

Relativity and... quantum... remain incomplete. ...the main reason each is incomplete is the existence of the other. The mind calls for a third theory to unify all of physics, and for a simple reason. Nature is... "unified." …interconnected, in that everything interacts with everything else.

From the beginning of physics, there have been those who imagined they would be the last generation to face the unknown. Physics has always seemed to its practitioners to be almost complete. This complacency is shattered only during revolutions, when honest people are forced to admit that they don't know the basics.