Buridan's ass is the common name for the paradox which states that an entirely rational ass, placed between two stacks of hay of equal size and quality, will starve since it cannot make any rational decision to start eating one rather than the other. The paradox is named after the 14th century French philosopher Jean Buridan.
The paradox was, however, not originated by Buridan himself. It is first found in Aristotle's De Caelo where Aristotle asked how a dog faced with the choice of two equally tempting meals could rationally choose between the two. 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 in order more fully to assess the possible outcomes of the choice. Later writers satirised this view in terms of an ass who, confronted by two equally desirable and accessible bales of hay, must necessarily starve while pondering a decision.
Another context where the paradox surfaces is as an attempted justification for faith. The argument is that, like the starving ass, we must make a non-rational choice in order to avoid being frozen in endless doubt. 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 pick one instead of starving. Other counter-arguments exist.
There's a new Wal-Mart in my neighborhood; a ghastly huge edifice with a ghastly huge Pacific Northwest style parking lot (too many weird curbs) that could theoretically supply most stuff I need; I can walk to the damn thing; its closer than the D'Agostino's from which I used to walk 4 city blocks (avenue-wise) to buy my groceries when I lived between York and East End avenues.
Of course, it's Wal-Mart.
And the alternative is driving my car to get stuff.
It's not really that kind of a problem; we buy lots of Chinese groceries, and there's really no way Wal-mart would substitute for everything we buy, despite their ghastly hugeness. Moreover, it does rain here continuously at times; walking to Wal-Mart really isn't an option those times.
But for some folks, some times, it could be: either use lots of gas to get milk and eggs or walk to Wal-Mart (assuming their milk and eggs aren't exactly hormone tainted crapola with mad-cow potential).
Wal-Mart will pass; their "always low prices" will pass.
I'll pass on Wal-Mart; hopefully other stores will develop in their vicinity (there's lots of unused commercial space at the moment.)