Before I present the proof, recall the following. P -> Q is true whenever P is false or Q is true. Recall also that modus tollens is a valid form of argument:
P -> Q
Not-Q.
Therefore, not-P.
So, then, here is the proof:
(1) If God does not exist, then it is not the case that if I am evil, I will be punished after I die.
(2) I am not evil.
(3) Therefore, God exists.
😛
Originally posted by LemonJelloExcept that (2) is not the same as the consequent of (1). If I am not evil, then the conditional 'If I am not evil, I will be punished after I die' is trivially true. It's not modus tollens.
Before I present the proof, recall the following. P -> Q is true whenever P is false or Q is true. Recall also that modus tollens is a valid form of argument:
P -> Q
Not-Q.
Therefore, not-P.
So, then, here is the proof:
(1) If God does not exist, then it is not the case that if I am evil, I will be punished after I die.
(2) I am not evil.
(3) Therefore, God exists.
😛
Originally posted by Conrau KI think you made a typo in the antecedent of your conditional.
Except that (2) is not the same as the consequent of (1). If I am not evil, then the conditional 'If I am not evil, I will be punished after I die' is trivially true. It's not modus tollens.
At any rate, it is modus tollens. Take another look at the full consequent of (1).
Originally posted by LemonJellohttp://i0.kym-cdn.com/photos/images/original/000/131/351/eb6.jpg?1307463786
Before I present the proof, recall the following. P -> Q is true whenever P is false or Q is true. Recall also that modus tollens is a valid form of argument:
P -> Q
Not-Q.
Therefore, not-P.
So, then, here is the proof:
(1) If God does not exist, then it is not the case that if I am evil, I will be punished after I die.
(2) I am not evil.
(3) Therefore, God exists.
😛
Originally posted by LemonJellothe only mystery about the "proof" is whether you thought of it as a joke(aka trolling) or you had a brain fart (aka stupid) and you actually believe you came up with something intelligent.
Tell me precisely what is wrong with the proof. I know what the problem is here; do you?
either way, it is illogical.
Originally posted by ZahlanziIf it is illogical, then please point out where the logic fails.
the only mystery about the "proof" is whether you thought of it as a joke or you had a brain fart and you actually believe you came up with something intelligent.
either way, it is illogical.
Anyway, I did not come up with this proof. A person much smarter than I came up with it. I think it can be an instructive exercise to try to figure out why it fails.
Originally posted by LemonJelloinstructive exercise? for something this poorly constructed? are you kidding?
If it is illogical, then please point out where the logic fails.
Anyway, I did not come up with this proof. A person much smarter than I came up with it. I think it can be an instructive exercise to try to figure out why it fails.
i ask again, are you trolling? the alternative to this might be more embarrassing for you.
Originally posted by ZahlanziI repeat: if it is illogical, then please point out where the logic fails. And please be specific.
instructive exercise? for something this poorly constructed? are you kidding?
i ask again, are you trolling? the alternative to this might be more embarrassing for you.
Originally posted by LemonJelloi fed the troll. i am ashamed.
I repeat: if it is illogical, then please point out where the logic fails. And please be specific.
please feel free to congratulate yourself for provoking me into 3 posts in a trolling thread.
or feel free to assume i am ignorant of logic and jealous of your awesome intellect if you are sincere in wanting to debate this.
Originally posted by ZahlanziSo you are unwilling (or unable) to back up your claim that the proof I presented is illogical?
i fed the troll. i am ashamed.
please feel free to congratulate yourself for provoking me into 3 posts in a trolling thread.
or feel free to assume i am ignorant of logic and jealous of your awesome intellect if you are sincere in wanting to debate this.
You get a FAIL.
Originally posted by LemonJelloBasically what I mean to say is that the conditional is trivially false and modus tollens does not apply.
I think you made a typo in the antecedent of your conditional.
At any rate, it is modus tollens. Take another look at the full consequent of (1).
As I see it, there are three propositions:
P -- God exists
Q -- I am evil
R -- I will be punished after I die.
So the proof runs like this:
(1) ~P --> ~(Q-->R)
(2) ~Q
Therefore,
(3) P.
If ~Q, however, then Q-->R is trivially true, so the consequent ~(Q-->R) is trivially false.
Under the same logic, you can mount a proof of anything. Basically it's a failure of relevance logic, like saying 'If the world will end, then 2+2 =4'.
So, as far as propositional calculus goes, it is logical.
Reductio ad absurdum:
(1) ~P --> ~(Q-->R)
(2) ~Q
Therefore,
(3) ~P. (i.e. God does not exist)
From (1)
~~P or ~(Q-->R)
so,
P or (Q and ~R)
But (Q and ~R) contradicts (2) ~Q.
But P contradicts (3) ~P.
I think the failure must be relevance, the fact that we are dealing with truth triviality. We get the same triviality if we assert R, I will be punished after I die. So if I will be punished after I die, then (Q-->R) is trivially true and so ~(Q-->R) false and therefore ~P is false, so P, God must exist.
Originally posted by Conrau KYes, very good. You've proven yourself much more worthy than our friend Zahlanzi.
Basically what I mean to say is that the conditional is trivially false and modus tollens does not apply.
As I see it, there are three propositions:
P -- God exists
Q -- I am evil
R -- I will be punished after I die.
So the proof runs like this:
(1) ~P --> ~(Q-->R)
(2) ~Q
Therefore,
(3) P.
If ~Q, however, then Q-->R is trivially ...[text shortened]... asically it's a failure of relevance logic, like saying 'If the world will end, then 2+2 =4'.
I do not think the problem here involves any mis-application of modus tollens. But I would agree that the problem is related to the subject of relevance logic. The problem here must lie in how it treats an indicative conditional like 'If I am evil, I will be punished after I die' and bases it in the truth functionality of a material conditional.
Originally posted by LemonJelloThe problem here must lie in how it treats an indicative conditional like 'If I am evil, I will be punished after I die' and bases it in the truth functionality of a material conditional.
Yes, very good. You've proven yourself much more worthy than our friend Zahlanzi.
I do not think the problem here involves any mis-application of modus tollens. But I would agree that the problem is related to the subject of relevance logic. The problem here must lie in how it treats an indicative conditional like 'If I am evil, I will be punished after I die' and bases it in the truth functionality of a material conditional.
Yes, that sums it up. It was nothing to do with modus tollens per se. Thank you for that interesting piece of logic.