Buridan's ass

Political cartoon ca. 1900, showing the United States Congress as Buridan's ass, hesitating between a Panama route or a Nicaragua route for an Atlantic-Pacific canal.

Buridan's ass is an illustration of a paradox in philosophy in the conception of free will.

It refers to a hypothetical situation wherein an ass, placed precisely midway between a stack of hay and pail of water, will die of both hunger and thirst since it cannot make any rational decision to choose one over the other.^[1] The paradox is named after the 14th century French philosopher Jean Buridan, whose philosophy of moral determinism it satirises.

History

The paradox did not originate in Buridan's time; it dates to antiquity, being first found in Aristotle's De Caelo, where Aristotle mentions an example of a man who makes no move because he is as hungry as he is thirsty and is positioned exactly between food and drink.

Buridan nowhere discusses this specific problem, but its relevance is that he did advocate a moral determinism whereby, save for ignorance or impediment, a human faced by alternative courses of action must always choose the greater good. Buridan allowed that the will could delay the choice to more fully assess the possible outcomes of the choice. Later writers satirised this view in terms of an ass which, confronted by both food and water must necessarily die of both hunger and thirst while pondering a decision.

A common variant substitutes two identical piles of hay for both hay and water and advances that the ass, unable to choose between the two, dies of hunger alone.^[2]

Discussion

Some proponents of hard determinism have granted the unpleasantness of the scenario, but have denied that it illustrates a true paradox, as such, since one does not contradict oneself in suggesting that a man might die between two equally plausible routes of action. For example, Baruch Spinoza in his Ethics, suggests that a person who sees two options as truly equally compelling cannot be fully rational:

[I]t may be objected, if man does not act from free will, what will happen if the incentives to action are equally balanced, as in the case of Buridan's ass? [In reply,] I am quite ready to admit, that a man placed in the equilibrium described (namely, as perceiving nothing but hunger and thirst, a certain food and a certain drink, each equally distant from him) would die of hunger and thirst. If I am asked, whether such an one should not rather be considered an ass than a man; I answer, that I do not know, neither do I know how a man should be considered, who hangs himself, or how we should consider children, fools, madmen, &c.

– Baruch Spinoza, Ethics, Book 2, Scholium

Other writers have opted to deny the validity of the illustration. A typical counter-argument is that rationality as described in the paradox is so limited as to be a straw man of the real thing, which does allow the consideration of meta-arguments. In other words, it's entirely rational to recognize that both choices are equally good and arbitrarily (randomly) pick one instead of starving. This counter-argument is sometimes used as an attempted justification for faith or intuitivity (called by Aristotle noetic or noesis). The argument is that, like the starving ass, we must make a choice in order to avoid being frozen in endless doubt. Other counter-arguments exist.

Application to digital logic: metastability

A version of the Buridan's ass dilemma actually occurs in electrical engineering. Specifically, in digital logic, an analog-to-digital converter must convert a continuous voltage value into either a 0 or a 1. The voltage value represents the position of the ass, and the values 0 and 1 represent the bales of hay. Like the situation of the starving ass, there exists an input on which the converter cannot make a proper decision, resulting in a metastable state. Having the converter make an arbitrary choice in ambiguous situations does not solve the problem, as the boundary between ambiguous values and unambiguous values introduces another binary decision with its own metastable state.

Addition of hysteresis and a default state in the design, however, does resolve the Buridan's ass dilemma. Hysteresis in this context would intentionally change state from 0 to 1 at a different point than 1 to 0 so that the midpoint value would be defined by the previous value(or the default).

See also

• Catch-22
• Dining philosophers problem
• Entropy
• Hobson's choice
• Metastability in electronics
• Morton's fork
• Spontaneous symmetry breaking

References

Bibliography

• The Columbia Encyclopedia, Sixth Edition (2006)
• Elizabeth Knowles (2006). "The Oxford Dictionary of Phrase and Fable"
• Rescher, Nicholas (1959/60). 'Choice Without Preference: A Study of the History and of the Logic of the Problem of “Buridan’s Ass”'. Kant-Studien, vol. 51, pp. 142-75.
• Zupko, Jack (2003). John Buridan: Portrait of a Fourteenth-Century Arts Master. Notre Dame, Indiana: University of Notre Dame Press. (cf. pp. 258, 400n71)

External links

• Competing interactions create functionality through frustration, Vassiliy Lubchenko, PNAS August 5, 2008 vol. 105 no. 31 10635-10636