Morton's fork

Morton's fork is the term given to a tricky bit of sophistry in which a conclusion is drawn in several different ways that contradict each other. It is named after Cardinal John Morton (Henry VII of England's sidekick). Morton was a tax collector. If someone was lavish in their spending, it was proof that they were rich and could afford to pay what was asked; if they were less forthcoming, it was evidence that they must have a great deal of savings from living such an austere lifestyle, and hence could likewise afford to pay. However, in Morton's defense, this tactic was primarily intended for prying money out of the clutches of tax-dodging Monopoly Men who were already known to be rich (some things never change, do they?).

Variations of this are often used by creationists, who will use any observation, as well as its inverse, as "proof" of Biblical literalism. This is also a favorite of conspiracy theorists, who believe evidence against the conspiracy is actually evidence for the conspiracy because those perpetrating the conspiracy are obviously covering up the necessary evidence.

This fallacy can be neatly summed up by the phrase "Heads, I win; Tails, you lose."

Eliezer Yudkowsky discusses this fallacy when formulating what he calls the law of conservation of expected evidence: if data D is considered evidence for hypothesis H, then the opposite data ~D must be considered evidence against hypothesis H. In this sense, evidence-based reasoning is different from deductive reasoning (formal logic-based), where $$P \Rightarrow Q$$ does not imply $$\neg P \Rightarrow \neg Q$$.

Fine Tuning Argument
The Fine Tuning Argument attempts to prove the existence of a god by showing that the likelihood of a universe arising in which our life is supported is so small that our existence in a universe that supports us shows something must have created the universe for us. Essentially it states that because we are in a universe which can support our life, but it seems likely that most "possible" universes could not support our life, a god must have ensured this universe supports our life.

However, if we existed in any of the multitude of "possible" universes that clearly shouldn't support our life, this would then become evidence that some god had somehow protected us so we formed despite all possibilities, rather than the universe forming to support us despite all the possibilities. So either a god exists because we are in one of the few and rare "possible" universes that can support our life without a god, or a god exists because we are in one of the many universes that can't support our life without a god.

Witchcraft
During many periods of history, including the Salem Witch Trials, the European witch-hunts, and the McCarthy Era, the question has been posed to anyone presumed guilty of a crime: if they did confess, then they would be relieved of their belongings (which would, more often than not, end up with their accuser) and set free to die on their own, whereas if they declared themselves innocent, they would be tortured to death, then relieved of their belongings, as a truly guilty person would never confess. This was later applied in Arthur Miller's play, which while set during the period of the Salem Witch Trials, was allegorical for the then-contemporary McCarthyism.

Other examples are listed by, a German priest who opposed witch hunts, in his 1631 work Cautio Criminalis. If a woman led an evil and improper life, it was considered proof that she was a witch; if she led a good and proper life, this was also considered evidence that she was a witch, because witches try to appear virtuous.

In fiction
A well-known example occurs in the comedy film  when the protagonist, an ordinary Jewish man in 1st century Jerusalem who accidentally gathers a crowd of religious devotees, tries to convince them that he's not the Messiah.


 * Brian: I'm not the Messiah! Will you please listen? I'm not the Messiah! Do you understand? Honestly!
 * Followers: Only the true Messiah denies his divinity.
 * Brian: What? Well, what sort of chance does that give me? All right, I am the Messiah!
 * Followers: He is! He is the Messiah!

Alternate Interpretation
The term "Morton's Fork" is also sometimes used more broadly to refer to any situation where one party can choose between a number of courses of action, none of which have a favorable result. I.e. "damned if you do, damned if you don't." Examples:
 * The Nuremburg Defense ("I was just following orders") has sometimes been, well, defended by pointing out that the soldiers using it were put in such a situation the instant they were given those orders: Eithr they could maybe be punished later for committing a war crime if they lost, or they could definitely be punished now for, you know, disobeying a direct order.


 * In 2011 a twenty year old woman claimed she'd been knocked up by Bieber the year before and sued him for compensation. The dumbass would've been sent to jail regardless of how the case turned out, since Bieber would've been underage at the time: if she lost, for fraud; if she won, for having sex with a minor. The case quietly went away.


 * Woomeisters who flaunt "the world will end on this specific date" predictions tend to realize all too late that they've impaled themselves on Morton's long, pointy fork. Either they turn out to be right, in which case they're probably dead along with everyone else, or they turn out to be wrong, in which case their credibility is permanently ruined.

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