If you want to draw a conclusion, you must not let it be foreseen, but
you must get the premisses admitted one by one, unobserved, mingling
them here and there in your talk; otherwise, your opponent will
attempt all sorts of chicanery. Or, if it is doubtful whether your
opponent will admit them, you must advance the premisses of these
premisses; that is to say, you must draw up pro-syllogisms, and get
the premisses of several of them admitted in no definite order.
In this way you conceal your game until you have obtained all the
admissions that are necessary, and so reach your goal by making a
circuit. These rules are given by Aristotle in his _Topica_, bk.
viii., c. 1. It is a trick which needs no illustration.