Mathematics is the only true metaphysics.

Science is bound, by the everlasting vow of honour, to face fearlessly every problem which can be fairly presented to it.

I can never satisfy myself until I can make a mechanical model of a thing. If I can make a mechanical model, I can understand it. As long as I cannot make a mechanical model all the way through I cannot understand.

In science there is only physics; all the rest is stamp collecting.

Simplification of modes of proof is not merely an indication of advance in our knowledge of a subject, but is also the surest guarantee of readiness for farther progress.

If we can't express what we know in the form of numbers, we really don't know much about it.

Quaternions came from Hamilton after his really good work had been done, and though beautifully ingenious, have been an unmixed evil to those who have touched them in any way.