Ya take off ur shirt
This is a discussion on The Squid argument: Valid? not valid? within the Member Polls forums, part of the Personality Type Forums category; Ya take off ur shirt...
Ya take off ur shirt
So it appears people either didn't take logic 101 or slept on the course. By definition, the validity of an argument does not require that the premises do not contradict one another, but that it is not possible for the conclusion to be false while the premises are true. If there is a contradiction in the premises then the argument is always valid, since from a contradiction any proposition can be derived.
Let the predicates S, G and L be Squid, Giraffe and Elephant respectively and j be Joe
1. Ax : Sx -> ~Gx
2. Ax : Gx -> ~Lx
3. Ax : Lx -> ~Sx
4. Sj v Gj
6. Ax : ~~Lx -> ~Gx (2, contraposition)
7. Ax : Lx -> ~Gx (6, double negation)
8. Lj -> ~Gj (7, substitution)
9. ~Gj (8, 5, modus ponens)
10. ~Gj ^ (Sj v Gj) (4, 9)
11. (~Gj ^ Sj) v (~Gj ^ Gj) (10, distributivity of ^ over v)
12. (~Gj ^ Sj) v F (law of non contradiction)
13. ~Gj ^ Sj (12, idempotence of F for v)
14. Sj (13, conjunction elimination)
Please note that I specified from the start that I was interested in whether posters personally accepted the argument as valid, not whether they had taken logic 101. I'm not sure why anyone would want to know that.
So, whether people took 101 is irrelevant. I'm interested in what they think, like, by themselves.
Further, I don't know of any rationale to dismiss the answers given by the other posters as incorrect.
You will also observe that in the other argument, the Monkey argument, 7 posters out of 7 give the same answer (and I would agree with their answer). Do you really think they don't know what a valid argument is?
But again, I didn't ask posters what was, or what they thought was, the definition of validity. So, again, that's irrelevant.
But, anyway, thank you for casting vote.
So, we still have only 2 votes for "valid" against 12 for "not valid" and 3 for "doesn't make sense".
Last edited by Speakpigeon; 08-17-2019 at 09:09 AM.
I accept that it's valid because there is no postulate that says a squid couldn't be an elephant. Using the idea that the logic must follow in the flow from left to right as it is written, squid and elephant are not mutually exclusive according to the first line. It only says that if one is an elephant first that they cannot be a squid in line three.
Since he is a squid or a giraffe (line 4), this is more important in the hierarchy of the argument than that he is an elephant (line 5).
This problem reminds me a lot of Asimov's laws of robotics in I, Robot (the book, not the movie), where various robots are put into different situations where the laws of robotics contradict themselves and the robots have to figure out which law is more important.
I must say that the hierarchy of statements is implied rather than stated straight out, though, so I'm taking an intuitive leap.
Since I saw you ask someone the same question in the other thread, I'd give this a 4/5 certainty (to being valid) whereas I'd give the monkey one a 5/5 certainty to being invalid.
Afterthought: I used something like the order of operations in maths to come to my conclusion.
Since someone else brought it up, I'd say the argument is valid but not sound, but that's thinking about it in a way that was specifically asked NOT to do.
Last edited by brightflashes; 08-18-2019 at 08:29 AM. Reason: Afterthought