It is a sound maxim, and one which all close thinkers have felt, but which no one before Bentham ever so consistently applied, that error lurks in generalities: that the human mind is not capable of embracing a complex whole, until it has surveyed and catalogued the parts of which that whole is made up; that abstractions are not realities per se, but an abridged mode of expressing facts, and that the only practical mode of dealing with them is to trace them back to the facts (whether of experience or of consciousness) of which they are the expression.
Proceeding on this principle, Bentham makes short work with the ordinary modes of moral and political reasoning. These, it appeared to him, when hunted to their source, for the most part terminated in phrases. In politics, liberty, social order, constitution, law of nature, social compact, &c., were the catch-words: ethics had its analogous ones. Such were the arguments on which the gravest questions of morality and policy were made to turn; not reasons, but allusions to reasons; sacramental expressions, by which a summary appeal was made to some general sentiment of mankind, or to some maxim in familiar use, which might be true or not, but the limitations of which no one had ever critically examined.
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It is the introduction into the philosophy of human conduct, of this method of detail—of this practice of never reasoning about wholes until they have been resolved into their parts, nor about abstractions until they have been translated into realities—that constitutes the originality of Bentham in philosophy, and makes him the great reformer of the moral and political branch of it.
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Instead of taking up their opinions by intuition, or by ratiocination from premises adopted on a mere rough view, and couched in language so vague that it is impossible to say exactly whether they are true or false, philosophers are now forced to understand one another, to break down the generality of their propositions, and join a precise issue in every dispute.
John Stuart Mill, “Bentham”, on reductionism and rationalist taboo