A mule which will gallop for a half-mile in the single direction elected by its rider even one time becomes a neighborhood legend; one that will do it consistently time after time is an incredible phenomenon. Because, unlike a horse, a mule is far too intelligent to break its heart for glory running around the rim of a mile-long saucer. In fact, I rate mules second only to rats in intelligence, the mule followed in order by cats, dogs, and horses last—assuming of course that you accept my definition of intelligence: which is the ability to cope with environment: which means to accept environment yet still retain at least something of personal liberty.

The rat of course I rate first. He lives in your house without helping you to buy it or build it or repair it or keep the taxes paid; he eats what you eat without helping you raise it or buy it or even haul it into the house; you cannot get rid of him; were he not a cannibal, he would long since have inherited the earth. …

The mule I rate second. But second only because you can make him work for you. But that too only within his own rigid self-set regulations. He will not permit himself to eat too much. He will draw a wagon or a plow, but he will not run a race. He will not try to jump anything he does not indubitably know beforehand he can jump; he will not enter any place unless he knows of his own knowledge what is on the other side; he will work for you patiently for ten years for the chance to kick you once. In a word, free of the obligations of ancestry and the responsibilities of posterity, he has conquered not only life but death too and hence is immortal; were he to vanish from the earth today, the same chanceful biological combination which produced him yesterday would produce him a thousand years hence, unaltered, unchanged, incorrigible still within the limitations which he himself had proved and tested; still free, still coping. …