I don't believe that the ultimate theory will come by steady work along existing lines. We need something new. We can't predict what that will be or when we will find it because if we knew that, we would have found it already!

If the total energy of the universe must always remain zero, and it costs energy to create a body, how can a whole universe be created from nothing?

We are in danger of destroying ourselves by our greed and stupidity. We cannot remain looking inwards at ourselves on a small and increasingly polluted and overcrowded planet.

I'm not afraid of death, but I'm in no hurry to die. I have so much I want to do first.

A theory is a good theory if it satisfies two requirements: it must accurately describe a large class of observations on the basis of a model that contains only a few arbitrary elements, and it must make definite predictions about the results of future observations.

Maybe I'm being a bit harsh on philosophers, but they have not been very kind to me... I have been variously called nominalist, an instrumentalist, a positivist, a realist, and several other ists. The technique seems refutation by denigration: If you can attach a label to my approach, you don't have to say what is wrong with it... I am sure that Einstein, Heisenberg and Dirac didn't worry about whether they were realists or instrumentalists.

Any physical theory is always provisional, in the sense that it is only a hypothesis: you can never prove it.