A scientist is never certain. ... We absolutely must leave room for doubt or there is no progress and there is no learning.

When it came time for me to give my talk on the subject, I started off by drawing an outline of the cat and began to name the various muscles. The other students in the class interrupt me: "We *know* all that!" "Oh," I say, "you *do*? Then no *wonder* I can catch up with you so fast after you've had four years of biology." They had wasted all their time memorizing stuff like that, when it could be looked up in fifteen minutes.

Words can be meaningless. If they are used in such a way that no sharp conclusions can be drawn.

I don't think that the laws can be considered to be like God because they have been figured out.

So, ultimately, in order to understand nature it may be necessary to have a deeper understanding of mathematical relationships. But the real reason is that the subject is enjoyable, and although we humans cut nature up in different ways, and we have different courses in different departments, such compartmentaliz ation is really artificial, and we should take our intellectual pleasures where we find them.

A philosopher once said, 'It is necessary for the very existence of science that the same conditions always produce the same results.' Well, they don't!

We never are definitely right, we can only be sure we are wrong.