The Life and Opinions of Tristram Shandy, Gentleman

Though man is of all others the most curious vehicle, said my father, yet at the same time 'tis of so slight a frame, and so totteringly put together, that the sudden jerks and hard jostlings it unavoidably meets with in this rugged journey, would overset and tear it to pieces a dozen times a day -- -- -was it not, brother Toby, that there is a secret spring within us.

-- Which spring, said my uncle Toby, I take to be Religion.