Poisoning the well
Poisoning the well (or attempting to poison the well) is a rhetorical device where adverse information about a target is pre-emptively presented to an audience, with the intention of discrediting or ridiculing everything that the target person is about to say. Poisoning the well can be a special case of argumentum ad hominem, and the term was first used with this sense by John Henry Newman in his work Apologia Pro Vita Sua (1864). The origin of the term lies in well poisoning, an ancient wartime practice of pouring poison into sources of fresh water before an invading army, to diminish the attacking army's strength.
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 her friend's opinion of the dress, she has "poisoned the well", as her previous comment could affect her friend's response.
An even simpler example of poisoning the well is by tautology and definition, or circular reasoning. This is similar to equivocation, where the use of words communicate a confusing meaning (often called a subtle lie). For example, if one starts an argument with "Everything I say is correct, no matter what you say", the well is poisoned and nothing a person says (be it true or false) will matter by the initiator's definition. An example of this rhetorical strategy is attributed to Michel Foucault by John Searle, regarding philosopher Jacques Derrida: "Michel Foucault once characterized Derrida's prose style to me as "obscurantisme terroriste." The text is written so obscurely that you can't figure out exactly what the thesis is (hence "obscurantisme") and then when one criticizes it, the author says, "Vous m'avez mal compris; vous êtes idiot" [roughly, "You misunderstood me; you are an idiot"] (hence "terroriste")."
A poisoned-well "argument" has the following form:
- 1. Unfavorable information (be it true or false, relevant or irrelevant) about person A (the target) is presented by another. (e.g., "Before you listen to my opponent, may I remind you that he has been in jail.")
- 2. Implicit conclusion: "Therefore, any claims made by person A cannot be relied upon".
- A subcategory of this form is the application of an unfavorable attribute to any future opponents, in an attempt to discourage debate. (For example, "That's my stance on funding the public education system, and anyone who disagrees with me hates children.") Any person who steps forward to dispute the claim will then risk applying the tag to him or herself in the process.
A poisoned-well "argument" can also be in this form:
- 1. Unfavorable definitions (be it true or false) which prevent disagreement (or enforce affirmative position)
- 2. Any claims without first agreeing with above definitions are automatically dismissed.
See also 
- Ad hominem
- Appeal to ridicule
- Black propaganda
- Fruit of the poisonous tree
- Guilt by association
- Scorched earth