Talk:Existential fallacy

The value of all this seems similar to learning ancient Greek to better understand the old writers. Consider "Every unicorn definitely has a horn on its forehead". In modern English, this is unclear. Perhaps the writer meant to say something closer to "Every imagined unicorn has exactly one forehead with exactly one horn." Now, if its horn is ground down one mm at a time to make magic powder, at what point does it cease to be a unicorn? 96.81.175.113 (talk) 16:16, 17 June 2016 (UTC)

"Traditional formal logic assumes that classes of things referred to in a logical statement are non-empty" seems patently untrue to me, so I deleted it. Empty predicates are certainly allowed in any formal logic I have seen. Perhaps the confusion lies in the assumption that the domain of discourse is non-empty, but this is irrelevant anyhow.

IIRC, the Boolean and Aristotelian views of existential fallacy differ (this article, again IIRC, addresses the Boolean view)...maybe include a link to explain existential import? 70.106.137.206 22:49, 27 October 2005 (UTC)

I probably know less about this than the previous authors, but isn't this sort of argument valid, but unsound?--Dustin Asby 05:52, 27 August 2005 (UTC)

"Valid" meaning "it is a correct syllogism if its premises are correct" and "sound" meaning "it is a correct syllogism and its premises are correct"? Yes, that's correct from my understanding (and I tutored people for a logic course back in college, so I think I'm probably on the ball with this one.)

However, the existential fallacy is a little different from most fallacies in that fallacies generally are a way to get from correct premises to an incorrect conclusion, where the existential fallacy can start with technically correct premises and arrive at a correct conclusion, but still induce people into incorrect beliefs.

For instance, if I present the following syllogism:

• Each snuff film made represents at least one act of murder for profit;
• Murder for profit is a capital offense;
• Therefore making a snuff film is a capital offense

I may convince the audience that my syllogism is valid -- and it is. However, even though I did not say anything untruthful, I may know that they will incorrectly assume from my words that snuff films actually exist.

Ironically, depending on interpretation, one could argue that a syllogism which commits the existential fallacy is still not only valid but also sound! One of the premises of symbolic logic that most people find surprising is that a statement in the form "if P, then Q" is always true when P is false. The statement "If the moon is solid silver, I am Queen of France" is actually true -- the only way it could be incorrect is if the moon was solid silver and I was not Queen of France. One could argue, then, that any syllogism which posits something about a class which is empty cannot be falsified. -- Antaeus Feldspar 17:33, 27 August 2005 (UTC)

So to prove an argument has commited the existential fallacy one must first know that the conclusion is false? It still seems to me that the term "invalid" isn't appropriate.--Dustin Asby 23:36, 27 August 2005 (UTC)

The conclusion of the syllogism need not even be false. However, if an uncautious observer would be led to assume that one of the sets under discussion is non-empty and that assumption is not supported, the existential fallacy has been committed. Basically, there is an "enthymeme", an unstated premise of the syllogistic chain, and it is "there actually are members of set X". -- Antaeus Feldspar 16:58, 28 August 2005 (UTC)

Mathematically, any statement about an empty set is actually true. The statement "All existent unicorns are purple" is true, by vacuous assertion. Of course, one could view such a statement at the same level of a tautology, something that is so trivially true that it supplies no useful information. --Puellanivis 06:38, 30 July 2006 (UTC)

All and all make some? IIRC you can assert that if all A are B and all B are C all A are C, not just some A are C. Kuroune 04:30, 10 February 2006 (UTC)

This is correct, although not required. While the (all, all) -> all is a stronger statement than (all, all) -> some, the later is not actually incorrect, it's just less useful. Usually, in philosophy, and math, one would like to make the strongest assertion possible, although if someone wishes to artificially inflate their accuracy, then they can often use a weak example. I don't know if there is actually a term to describe someone making such a widely weak assertion simply to be accurate, but I certainly have used it for comedic effect. "Sheesh, when is the bus going to get here?" "Likely sometime between now and the heat death of the universe." The only reasonable response to such a weak statement would be "duh". While it's not a tautology, the likelihood is just so incredibly high that it may as well be. Perhaps a pseudotautology, or paratautology, I suppose. Anyways, I suppose I'm getting off topic. --Puellanivis 06:37, 30 July 2006 (UTC)

--

This entire fallacy hinges around particular/existential statements about sets which may be empty. The statement "some Martians are friendly" means "there exists at least one Martian which is friendly", and so it cannot be true if the set of Martians is empty. The syllogism can be corrected if the non-emptiness of the set of Martians is added to the argument as an extra premise, either directly, or if it follows from some other existential premise. That is to say, if any of the premises in the argument implies that the set which is involved in the conclusion is not-empty, then the argument is rescued from this problem. For instance: Some martians have antennae. All martians are aliens. Aliens with antennae are friendly. Thus, some Martians are friendly. Basically, the argument's validity must be independent of its interpretation in all possible universes. The Existential fallacy is one possible problem which causes an argument to fail to have a valid interpretation in some possible universe (that universe in which the relevant set is empty). The improved argument here works in the universe in which there are no Martians, because then the premise "Some Martians have antennae" is false in that world. In that universe, the argument is interpreted as having both a falsehood among its premises, and a false conclusion. This doesn't interfere with its validity; a fallacy exists when a falsehood is begged from truthful premises. —Preceding unsigned comment added by 192.139.122.66 (talk) 23:44, 14 August 2008 (UTC)

Not quite. You've still referred to some Martians, but have presented no evidence for the existence of Martians, so you've still committed the fallacy. You have to know some in order to sort out which features are specific to a subset of a class, whereas talking about an entire class (all or none), doesn't make that assumption, and thus is safe. —Preceding unsigned comment added by 203.29.140.193 (talk) 07:22, 16 June 2009 (UTC)

isn't this just the fallacy of complex question (only worded as a statement instead of a question)? it's like the "fallacy of complex argument". first-martians and unicorns must be argued. Then one can argue the aspects of martians and unicorns (if it is still relevant).

have you stopped beating your wife? first-that you were beating your wife to begin with must be argued. then one can argue if the beatings stopped (if it is still relevant). —Preceding unsigned comment added by 76.15.29.209 (talk) 05:06, 3 July 2009 (UTC)

because this is a statement instead of a question, the actual fallacy is called "begging the question". A statement within the premise has has not yet been agreed upon even though it has been asserted. —Preceding unsigned comment added by 76.15.29.209 (talk) 15:11, 9 July 2009 (UTC)

Different uses of A

The article currently says "some A is B" on one line, and on the next line "This is invalid if the A form lacks ...". Are these two different usages of the capital 'A' symbol? If so, would it be very easy to improve the article by replacing the A, B and C symbols with P, Q and R? Open4D (talk) 17:03, 10 February 2014 (UTC)

Dinosaur Example confusing!

I read the article. Didn't understand the existential fallacy in the dinosaur example. Why is it a fallacy to assume dinosaurs exist??? (my email a.reinheimer@gmail.com) 77.138.17.217 (talk) 04:18, 16 December 2018 (UTC)

Are there such thing as nonexistent objects?

According to Stanford Encyclopedia of Philosophy, the the statement that something has propeties implies it exists, and this is a logical and philisophical problem. Thoughts? — Preceding unsigned comment added by 2A02:C7F:86C:7100:438:6EA9:B92C:6BB3 (talk) 00:07, 29 January 2021 (UTC)