John Henry Newman on "Poisoning the Wells"

(Incidentally, with this passage Newman apparently coined the term as applied to this particular fallacy)

[...] I wish to impute nothing worse to Kingsley than that he has been furiously carried away by his feelings. But what shall I say of the upshot of all this talk of my economies and equivocations and the like? What is the precise work which it is directed to effect? I am at war with him; but there is such a thing as legitimate warfare: war has its laws; there are things which may fairly be done, and things which may not be done. I say it with shame and with stern sorrow;—he has attempted a great transgression; he has attempted (as I may call it) to poison the wells [...]

[...] what I insist upon here, now that I am bringing this portion of my discussion to a close, is this unmanly attempt of his, in his concluding pages, to cut the ground from under my feet;—to poison by anticipation the public mind against me, John Henry Newman, and to infuse into the imaginations of my readers, suspicion and mistrust of every thing that I may say in reply to him. This I call poisoning the wells.

"I am henceforth in doubt and fear," he says, "as much as any honest man can be, concerning every word Dr. Newman may write. How can I tell that I shall not be the dupe of some cunning equivocation? ... What proof have I, that by 'mean it? I never said it!' Dr. Newman does not signify, 'I did not say it, but I did mean it'?"

Well, I can only say, that, if his taunt is to take effect, I am but wasting my time in saying a word in answer to his foul calumnies; and this is precisely what he knows and intends to be its fruit. I can hardly get myself to protest against a method of controversy so base and cruel, lest in doing so, I should be violating my self-respect and self-possession; but most base and most cruel it is. We all know how our imagination runs away with us, how suddenly and at what a pace;—the saying, "Caesar's wife should not be suspected," is an instance of what I mean. The habitual prejudice, the humour of the moment, is the turning-point which leads us to read a defence in a good sense or a bad. We interpret it by our antecedent impressions. The very same sentiments, according as our jealousy is or is not awake, or our aversion stimulated, are tokens of truth or of dissimulation and pretence. There is a story of a sane person being by mistake shut up in the wards of a Lunatic Asylum, and that, when he pleaded his cause to some strangers visiting the establishment, the only remark he elicited in answer was, "How naturally he talks! you would think he was in his senses." Controversies should be decided by the reason; is it legitimate warfare to appeal to the misgivings of the public mind and to its dislikings? Any how, if Mr. Kingsley is able thus to practise upon my readers, the more I succeed, the less will be my success. If I am natural, he will tell them, "Ars est celare artem;" if I am convincing, he will suggest that I am an able logician; if I show warmth, I am acting the indignant innocent; if I am calm, I am thereby detected as a smooth hypocrite; if I clear up difficulties, I am too plausible and perfect to be true. The more triumphant are my statements, the more certain will be my defeat.

-John Henry Newman, Apologia Pro Vita Sua (1864) [bold type emphasis mine]