"It is demonstrable," said he, "that things cannot be otherwise than as they are; for all being created for an end, all is necessarily for the best end. Observe, that the nose has been formed to bear spectacles — thus we have spectacles. Legs are visibly designed for stockings — and we have stockings. Stones were made to be hewn, and to construct castles — therefore my lord has a magnificent castle; for the greatest baron in the province ought to be the best lodged. Cows were made produce milk — therefore they queue up to milk themselves. Consequently they who assert that all is well have said a foolish thing, they should have said all is for the best."
The cows that queue up to milk themselves - BBC News