Talk:Existential fallacy

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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)