Poisoning the well

Poisoning the well (also called the smear tactic) is a rhetorical technique and logical fallacy that uses the association of negative emotions to distract a subject from actual evidence in an argument.

Poisoning the well is an appeal to hate.

The usual method is to point out the unpleasant nature of the person making the opposing argument, in which case it is a special case of a personal attack or ad hominem. In general, "to poison the well" means to pre-provide any information that could produce a biased opinion of the reasoning, positive or negative.

It can be done subtly or quite blatantly. A subtle way of poisoning the well would be to use particular adjectives in introducing something that would influence people who are about to hear an argument. A good example would be introducing an argument that you disagree with by using the phrase 'Do you believe this rubbish?' The word 'rubbish' poisons the well.

In a more blatant display, someone can make an outright personal attack in an introduction. For example, asking people to remember that a person has been in prison before listening to their statements; the well is now "poisoned" because people are likely to distrust a person making an argument knowing that they're a convict, regardless of the reasoning that they put forward.