For All Practical Purposes

A professor, asked what he meant by the phrase ["for all practical purposes"] explained:

"Suppose all the young men in this class were to line up on one side of the room, and all the young ladies on the other. At a given signal, the two lines move toward each other, halving the distance between them. At a second signal, they move forward again, halving the remaining distance; and so on at each succeeding signal. Theoretically, the boys would never reach the girls; but actually, after a relatively small number of moves, they would be close enough for all practical purposes."

-C. Stanley Ogilvey, Fantasia Mathematica, ed. Clifton Fadiman, 284.