In order to obtain physical ideas without adopting a physical theory we must make ourselves familiar with the existence of physical analogies. By a physical analogy I mean that partial similarity between the laws of one science and those of another which makes each of them illustrate the other.

We are certainly not to relinquish the evidence of experiments for the sake of dreams and vain fictions of our own devising; nor are we to recede from the analogy of Nature, which is wont to be simple and always consonant to itself.

I tend to approach things from a physics framework. And physics teaches you to reason from first principles rather than by analogy.

The reason of this is that if you look at the movement of the wateryour eye will not be able to fix on anything, but its action is as that of things seen in your shadow when you are walking; for if the eyeat-tempt to distinguish the nature of the shadow, the wisps of strawor other things contained in it appear of rapid movement and it seems that these are much more swift to flee from the said shadow than the shadow is to proceed.

Nothing is easier than to admit in words the truth of the universal struggle for life, or more difficult, at least I have found it so, than constantly to bear this conclusion in mind.

If you are out to describe the truth, leave elegance to the tailor.