"Few of those who fill the world with books, have any pretensions to the hope either of pleasing or instructing. They have often no other task than to lay two books before them, out of which they compile a third, without any new material of their own, and with very little application of judgment to those which former authors have supplied."

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We come finally, however, to the relation of the ideal theory to real world, or "real" probability. If he is consistent a man of the mathematical school washes his hands of applications. To someone who wants them he would say that the ideal system runs parallel to the usual theory: "If this is what you want, try it: it is not my business to justify application of the system; that can only be done by philosophizing; I am a mathematician". In practice he is apt to say: "try this; if it works that will justify it".

— John Edensor Littlewood