Subtility

—L. By thus glorying in their resistance to the vice of Nature's law—if, indeed, anything natural be vicious—they become not only like inhuman and cruel beasts, but even like the devils whose pride and subtility they borrow.

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And that such their subtility might not be perceived, they made him a like paire of eares and nose of wax: wherfore you may see that the poore miser for lucre of a little mony sustained losse of his members.

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I cannot omit a subtility of one of those quack operators, with which he gulled the poor people to crowd about him, but did nothing for them without money.

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But these scruples, if not too intricate, are of too extensive consideration for my present purpose, nor are they such as generally occur in common life; and though casuistical knowledge be useful in proper hands, yet it ought by no means to be carelessly exposed, since most will use it rather to lull than awaken their own consciences; and the threads of reasoning, on which truth is suspended, are frequently drawn to such subtility, that common eyes cannot perceive, and common sensibility cannot feel them. 18.

Source: wiktionary