Poisoning the well is a logical fallacy where adverse information about someone is pre-emptively presented to an audience, with the intention of discrediting or ridiculing everything that person is about to say. Poisoning the well is a special case of argumentum ad hominem. The term was first used with this sense [1] by John Henry Newman in his Apologia Pro Vita Sua [2]. In dialectic, the term logical fallacy properly refers to a formal fallacy: a flaw in the structure of a deductive argument which renders the argument invalid. ... An audience is a group of people who participate in and experience or encounter a work of art, literature, theatre, music or academics in any medium. ... An ad hominem argument, also known as argumentum ad hominem (Latin, literally argument against the person) or attacking the messenger, involves replying to an argument or assertion by attacking the person presenting the argument or assertion rather than the argument itself. ... J H Newman age 23 when he preached his first Sermon John Henry Newman (February 21, 1801 – August 11, 1890) was an English convert to Catholicism, later made a cardinal. ... Apologia Pro Vita Sua (Latin, A defence of ones life) is the classic defence of the religious opinions of John Henry Newman, published in 1864 in response to what he saw as an unwarranted attack on Roman Catholic doctrine by Charles Kingsley. ...

This "argument" has the following form:

1. Unfavorable information (be it true or false) about person A is presented.

2. Therefore any claims person A makes will be false.

Examples:

Before you listen to my opponent, may I remind you that he has been in jail.

Don't listen to what he says, he's a lawyer.

Another popular example is the use of Wikipedia as a referance:

Many wikipedia articles have been criticized and found to contain errors.

Your using wikipedia as a source to prove your claim.

Therefore, your claim is unsupported.

Note that the burden of proof lies on whoever poisons the well to verify that this particular wikipedia referance contains factual errors related to the original claim. In the common law, burden of proof is the obligation to prove allegations which are presented in a legal action. ...

In general usage, poisoning the well is the provision of any information that may produce a biased result. For example, if a woman tells her friend "I think I might buy this beautiful dress." then asks how it looks, she has "poisoned the well", as her previous comment could affect her friend's response.

Similarly, in written work, an inappropriate heading to a section or chapter can create pre-bias. As an example:

The so-called "Theory" of Relativity

We now examine the theory of relativity...

which has already "poisoned the well" to a balanced argument. Theory has a number of distinct meanings in different fields of knowledge, depending on the context and their methodologies. ... In physics, the term relativity is used in several, related contexts: Galileo first developed the principle of relativity, which is the postulate that the laws of physics are the same for all observers. ...

See also

• Argumentum ad hominem
• Appeal to ridicule
• Guilt by association.