Proving too much

From RationalWiki

Proving too much is the logical error of drawing a conclusion that is too broad, conflicting with other propositions either known to be true^[1] or logically prerequisite to the proposition itself.

[edit] Some examples

• "Nothing you find on a wiki is true."

This proposition, proves too much by invalidating itself, because if true the statement is false, since it appears on a wiki.

• "Human beliefs stem from wish fulfillment not evaluation of evidence."

This proposition proves too much by discrediting itself, as it is a human belief, and therefore must be based on wish-fulfillment not evidence.

• "Statements which are not empirically testable are meaningless."

This proposition (otherwise known as logical positivism), proves too much by invalidating itself, because the statement itself is not empirically testable, and is therefore meaningless by its own criterion.

• "Nothing outside the Bible is trustworthy."

This proposition proves too much by invalidating itself because the proposition itself appears outside of the Bible.

• "There is no objective reality."

This proposition proves too much by invalidating itself because the statement tacitly makes an assertion about the objective world (i.e. if you believe there is an objective reality, you're making an objectively false statement).

• BEDEVERE: Tell me. What do you do with witches?

VILLAGER #2: Burn!

VILLAGER #1: Burn!

CROWD: Burn! Burn them up! Burn!...

BEDEVERE: And what do you burn apart from witches?

VILLAGER #1: More witches!

VILLAGER #3: Shh!

VILLAGER #2: Wood!

BEDEVERE: So, why do witches burn?; [pause];

VILLAGER #3: B--... 'cause they're made of... wood?

BEDEVERE: Good! Heh heh.

CROWD: Oh, yeah. Oh.

BEDEVERE: So, how do we tell whether she is made of wood?

VILLAGER #1: Build a bridge out of her.

BEDEVERE: Ah, but can you not also make bridges out of stone?

VILLAGER #1: Oh, yeah.^[2]

This dialogue contains two instances of proving too much. Villager #3's criterion for "Is it a witch?" is "does it share a characteristic with wood (something you burn)?" But of course we burn lots of things that aren't witches. Therefore it proves too much by conflicting with known facts (answering the challenge of footnote 1). Similarly, Villager #1 suggests that they should build a bridge out of her to see if she is made out of wood. However, Bedevere sagely points out that even if they could make a bridge out of her, she might also be made of stone.^[3]

• "Global anti-realism of this sweeping sort has one nasty consequence: it calls into question any reality claim the warrant for whose existence would be the explanatory success of the theories in which they appear. This would include, then, all historical theories, cosmology, evolutionary biology, palaeontology, all attempts to establish the sequence of events in the distant past as well as the sorts of entities that populated the universe long ago, or for that matter, not so long ago. Quod nimis probat, nihil probat; the medieval adage "what proves too much, proves nothing"^[4] comes immediately to mind.

[edit] Commentary

Since none of these examples make clear what is meant,^[5] let us now say what the error is. It is an attempt to somehow prove^[6] the existence of supernatural entities, and their involvement in human life, by whining^[7] about logical positivism and materialism as somehow flawed at their basic level.^[8]

Which is amusing, since they are the only tools that have ever proved useful in the attempt to understand the world around us.^{[citation needed]}

[edit] Footnotes

1. ↑ Name one (See example 6).
2. ↑ Monty Python and the Holy Grail
3. ↑ While this logical error is considered amusing in the context of witches and wood, it is somehow considered sage philosophy in the context of logical positivism.
4. ↑ In the Scope of Logic, Methodology and Philosophy of Science: Volume Two
5. ↑ Or any damn sense, for that matter.
6. ↑ Despite the absence of any reference to the supernatural or any identifiable arguments that it exists; in fact, the author does not believe the word "supernatural" holds any meaning.
7. ↑ Whining: v. 1) The act of criticizing my beliefs through logic when I lack the mental resources to understanding what is being said; 2) The act of defending your beliefs when I lack the mental resources to understand what you mean.
8. ↑ Which they might very well be.