"Fesapo" is one of the names in a medieval mnemonic device for identifying valid categorical syllogisms. Fesapo designates the syllogistic form EA0-4 because of the order and appearance of the vowels 'e', 'a', and 'o'. Fesapo commits the existential fallacy and so is considered only conditionally valid in modern logic.
Saturday, September 20, 2008
Homework Problems?
I've started this string as a default area for discussion of any homework problems (take-home or practice set). Alternatively, feel free to begin a string dedicated to a particular problem.
So, I have been working on Homework Week 6 problem number 4 for what seems like forever. And I have come to the conclusion that the tilda is the bane of logic... That said, here is where I am getting stuck if anyone has suggestion.
1. ~(D*E) A DEDUCE ~Dv~E 2. ~(~Dv~E) I don't actually know how to interpret line two into the two halves of the disjunct for the next line or for that matter, can I simplify line one at all?
Take a look at how we prove the LEM. In that proof, we also have to deal with a negated disjunction. Otherwise, CD is not an available strategy here (bc line 2 is a negation and NOT a disjunction... and similiarly with line 1. You can't use simp because you don't have a conjunction... -C
Here's another hint: from line 2, you should be able to derive that D and E (after all, that's what line 2 means). Now, if you know that from line 2, you can derive that D, then an additional provisional assumption of ~D for RAA should be able to get you a contradiction (and similarly for E). The trick, to the extent that there is one, is that you see this step by focusing on your line 2 provisional assumption and NOT the given premise. Hope one of these hints helps -C
3 comments:
So, I have been working on Homework Week 6 problem number 4 for what seems like forever. And I have come to the conclusion that the tilda is the bane of logic... That said, here is where I am getting stuck if anyone has suggestion.
1. ~(D*E) A DEDUCE ~Dv~E
2. ~(~Dv~E)
I don't actually know how to interpret line two into the two halves of the disjunct for the next line or for that matter, can I simplify line one at all?
Marie
Take a look at how we prove the LEM. In that proof, we also have to deal with a negated disjunction. Otherwise, CD is not an available strategy here (bc line 2 is a negation and NOT a disjunction... and similiarly with line 1. You can't use simp because you don't have a conjunction... -C
Here's another hint: from line 2, you should be able to derive that D and E (after all, that's what line 2 means). Now, if you know that from line 2, you can derive that D, then an additional provisional assumption of ~D for RAA should be able to get you a contradiction (and similarly for E). The trick, to the extent that there is one, is that you see this step by focusing on your line 2 provisional assumption and NOT the given premise. Hope one of these hints helps -C
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