Jean Buridan didn’t invent the donkey named after him as a counterexample to determinism. Since his principal contribution was in the field of mechanics, the donkey may be mods properly named in honor of Democritus, Leucippus, or Lucretius. The Stoics believed that the world was composed of atoms and that their motion and everything derived from their motion was entirely determined. The intuition was astute but the mathematics to describe their vision was lacking. The mathematical notation used by the Greeks was adequate to natural numbers of a limited size, but for huge numbers and for the fractions that fell between the natural numbers, this notation faltered. The place-value system that originated in India can represent such quantities with ease and precision, but without the benefit of these representations, quantities are much less finely set. The Stoics took their atoms to be very, very small but nevertheless of a finite size and, as their very name meant uncuttable, indivisible into smaller parts. In their description of reality, they were condemned to rely on finite quantities, and coarsely grained measurements, weaknesses exploited by their adversaries in the devising of counterexamples.
Buridan’s ass is a hungry donkey set between two piles of hay, one to the right, one to the left. The piles are exactly the same size, and they are exactly equidistant to the befuddled donkey between them. In our own age, we are so accustomed to the gargantuan numbers of astronomy, and the tiny intervals of particle physics that we find it incredible that distances or masses should be completely equal. We’ve learned to live without simultaneity, and so it’s easy for us to relinquish the precise equality of any measurements. Initial conditions are so finely set that the tiniest alteration will lead to drastically different outcomes, as Edward Lorenz discovered using the amplitude of place-value notation and computers. Montaigne suspected it without these aids.
It might rather, methinks, be said, that nothing presents itself to us wherein there is not some difference, however little soever; and that, either by the sight or the touch, there is always some choice, that, though it be imperceptibly, tempts and attracts us;
Setting chaos theory aside for a moment, there is also something peculiar about the psychology at work here. Again, in Montaigne’s words:
‘Tis a pleasant imagination, to fancy a mind exactly balanced between to equal desires.
The fancy imagines desire as having a certain mass, and it also imagines a central actor, an arbiter between these two desires and occupying some space between them. There is an ancient tradition that explains the emotions as the affects of humors, fluids which have different and sometimes contradictory influences on the mind and body. It is only a small step to take from thinking of the emotions as fluids to thinking of desire as a fluid as well. Desires may then be measured, poured into a flask and topping out at red lines with red numbers beneath. The arbiter in the middle of all this is similar to the homunculus debunked by Gilbert Ryle.
To say that somebody desires something, is to say that he will choose it over anything else. Desire isn’t some humor, some fuel that propels us toward certain objects. Desire is an act of preferring. It is impossible to think of an agent torn between two contradictory and equal desires, because desire is nothing more than choosing one thing and foregoing another. Desire can’t be quantified because it isn’t a measure but an indexing. The donkey will choose one pile of hay over the other. Some are lascivious and will pursue sex to the cost of their position. Some are avaricious and will pursue money over rank, some ambitious and will take rank and preeminence over wealth. Some are gluttonous and pick food over drink, some are drunkards and will rather drink than eat. The vain will take applause no matter what the cost, and the spiteful will forego their own acclaim for the humiliation of their enemies. These actors don’t make these choices because they are filled with twenty milliliters of rage but thirty milliliters of sloth and their sloth outweighs their rage and consequently they take no action when injured. We know them to be wrathful, slothful, envious, or greedy because of what they do and these are descriptions of their behavior and not some underlying humor.