We have found it of paramount importance that in order to progress, we must recognize our ignorance and leave room for doubt.

All theoretical chemistry is really physics; and all theoretical chemists know it.

Any schemes - such as 'think of symmetry laws', or 'put the information in mathematical form', or 'guess equations'- are known to everybody now, and they are all tried all the time. When you are stuck, the answer cannot be one of these, because you will have tried these right away...The next scheme, the new discovery, is going to be made in a completely different way.

All things are made of atoms - little particles that move around in perpetual motion, attracting each other when they are a little distance apart, but repelling upon being squeezed into one another. In that one sentence, you will see, there is an enormous amount of information about the world, if just a little imagination and thinking are applied.

I think a power to do something is of value. Whether the result is a good thing or a bad thing depends on how it is used, but the power is a value.

The test of all knowledge is experiment.

While I am describing to you how Nature works, you won't understand why Nature works that way. But you see, nobody understands that.