The fittest survive

The fittest survive.
What is meant by the fittest?
Not the strongest; not the cleverest–
Weakness and stupidity everywhere survive.
There is no way of determining fitness except in that a thing does survive.
“Fitness,” then, is only another name for “survival.”
Darwinism:
That survivors survive.

Charles Fort, The Book of the Damned, p24 (The Complete Books of Charles Fort, Dover, c1974).