If you find that you are being worsted, you can make a diversion – that is, you can suddenly begin to talk of something else, as though it had a bearing on the matter in dispute, and afforded an argument against your opponent. This may be done without presumption if the diversion has, in fact, some general bearing on the matter; but it is a piece of impudence if it has nothing to do with the case, and is only brought in by way of attacking your opponent.
For example, I praised the system prevailing in China, where there is no such thing as hereditary nobility, and offices are bestowed only on those who succeed in competitive examinations. My opponent maintained that learning, as little as the privilege of birth (of which he had a high opinion), fits a man for office. We argued, and he got the worst of it. Then he made a diversion, and declared that in China all ranks were punished with the bastinado, which he connected with the immoderate indulgence in tea, and proceeded to make both of them a subject of reproach to the Chinese. To follow him into all this would have been to allow oneself to be drawn into a surrender of the victory which had already been won. The diversion is mere impudence if it completely abandons the point in dispute, and raises, for instance, some such objection as “Yes, and you also said just now,” and so on. For then the argument becomes to some extent personal; of the kind which will be treated of in the last section. Strictly speaking, it is half-way between the argumentum ad personam, which will there be discussed, and the argumentum ad hominem.
How very innate this trick is, may be seen in every quarrel between common people. If one of the parties makes some personal reproach against the other, the latter, instead of answering it by refuting it, allows it to stand, – as it were, admits it; and replies by reproaching his antagonist on some other ground. This is a stratagem like that pursued by Scipio when he attacked the Carthaginians, not in Italy, but in Africa. In war, diversions of this kind may be profitable; but in a quarrel they are poor expedients, because the reproaches remain, and those who look on hear the worst that can be said of both parties. It is a trick that should be used only faute de mieux.
[See also section xviii]