The most attractive feature of poisoning the well is that the opposition is discredited before they have uttered a single word. At its crudest, the fallacy consists in making unpleasant remarks about anyone who might disagree with a chosen position. When some willing victim steps forward to dispute that position, he only shows that the unpleasant remarks apply to him,
Everyone except an idiot knows that not enough money is spent on education.
(When someone comes forward to suggest that enough money is being spent he identifies himself to the audience as the idiot in question.)
The whole discussion is fallacious because it invites acceptance or rejection of the proposition on the basis of evidence which has nothing to do with it. The claim is only an insult, offered without evidence, and does not have to be accepted. Even if it were true, we would still have to examine the argument on its merits.
Closer inspection shows that poisoning the well is a highly specialized version of the ad hominem abusive. Instead of insulting the arguer in the hope that the audience will be led to reject his argument the well-poisoner sets up the insult for any-one who might argue. It is cleverer than simple abuse because it invites the victim to insult himself by drinking from the poisoned well. In doing so, it discourages opposition.
Of course, there may be those with defective judgement who prefer buses to trains.
(There may be those who take into account such factors as price, cleanliness, convenience, and running on time. To admit the preference now, however, would be owning up to defective judgement.)
In its crude and simple form, poisoning the well is seen to be great fun and can engender spectacular coups of withering scorn. A version which is only slightly more subtle appears in a game called ‘sociology of knowledge’. To play the game, one player starts by asserting that everyone else’s view about society and politics is only the unconscious expression of their class interest. Next, he shows that for specialized reasons this analysis does not apply to him because he is unprejudiced and can see things objectively. When another player disagrees with any of his views, the first player triumphantly shows that the opinion of his opponent can be ignored as the mere expression of class interest.
Choice in education is only a device by which the middle classes can buy advantage for their children.
(There is no point now in pointing to any role which competition might play in improving standards, or to the advantages of allowing parents some say in the type of education given to their children. You have already been convicted of trying to buy advantage; the rest is just cover.)
Skilful use of poisoning the well should employ both of its main characteristics. The poison should not only incite ridicule from the audience, it should also act as a deterrent to anyone tempted to disagree with you. ‘Only an idiot’ will put off some, but there will be others who think they could shrug it off. A better poison would be one sufficiently dreadful or embarrassing to deter anyone from drinking willingly.
Only those who are sexually inadequate themselves now advocate single-sex teaching in our schools.
Well-poisoning is recommended whenever your claim might not survive sustained scrutiny. It is also useful for dealing with an opponent whose point goes against received opinion but is, unfortunately, valid. Judicious poisoning will make such an opponent look so foolish that people will ignore the validity. It will also make you look witty and confident, and may even serve to conceal the fact that you are wrong.