I did what you asked in the initial response, then repeated it and gave you a link explaining why I had the question. I furthered explained my problem your conclusion in my last response. All you've done so far is explain that modus tollens is valid. You haven't shown that your use of it is correct. If I were you, I'd spend more time defending my original essay and adding clarity to it than dealing with the details of propositional logic.You're agreeing that modus tollens is valid, right? So can you please explain how the argument in the essay can possibly not be an instance of modus tollens? Is the idea that you think that the "if... then" might not have the sense of classical logic? All that we need is that if p is true and q is false, then "if p then q" is false. That's all that is needed for the validity of the argument, and that is true on any interpretation of "if... then". I'm just not clear what your objection is, I'm afraid.
I did what you asked in the initial response, then repeated it and gave you a link explaining why I had the question. I furthered explained my problem your conclusion in my last response. All you've done so far is explain that modus tollens is valid. You haven't shown that your use of it is correct. If I were you, I'd spend more time defending my original essay and adding clarity to it than dealing with the details of propositional logic.You're agreeing that modus tollens is valid, right? So can you please explain how the argument in the essay can possibly not be an instance of modus tollens? Is the idea that you think that the "if... then" might not have the sense of classical logic? All that we need is that if p is true and q is false, then "if p then q" is false. That's all that is needed for the validity of the argument, and that is true on any interpretation of "if... then". I'm just not clear what your objection is, I'm afraid. I rarely say "read my post", but I've repeated myself twice. Just because your words fit in the pattern doesn't mean they are valid. If that were true, then you could claim to prove anything.
I rarely say "read my post", but I've repeated myself twice. Just because your words fit in the pattern doesn't mean they are valid. If that were true, then you could claim to prove anything.Well, I really apologise for the inconvenience, but I'm just not getting your point. I might even go so far as to accuse you of bad tutoring. I have read all your posts carefully, and I simply don't understand what your objection is. It seems to me you're not making yourself very clear. *Why* is it the case that just because my words fit the pattern doesn't mean it's a valid argument? That is the whole *point* of identifying a logical form with the property that every argument of this logical form is valid. And obviously the assertion "if that were true, then you could claim to prove anything" is completely false. I read your link, and it is a very fine explanation of what "if... then" in propositional logic means, and that is exactly what I mean. I have absolutely no idea why you think that the argument that I present in the essay is not deductively valid. Very sorry to be so obtuse.
Did you read the part in the link about “If I am elected the King of France, then I will make it rain ice cream”, is considered a valid construct? Once you consider the real world, it doesn’t help you much, but it’s still valid.
Why don’t you just move on to explaining your essay. Why do you give a different definition, then an argument against it, then refute the argument and claim that makes subjectivism, “still in play”. Wouldn’t it be more useful to use an existing definition and an existing argument and speak to those?
Did you read the part in the link about "If I am elected the King of France, then I will make it rain ice cream", is considered a valid construct? Once you consider the real world, it doesn't help you much, but it's still valid. Why don't you just move on to explaining your essay. Why do you give a different definition, then an argument against it, then refute the argument and claim that makes subjectivism, "still in play". Wouldn't it be more useful to use an existing definition and an existing argument and speak to those?With regard to your example "If I am elected the King of France, then I will make it rain ice cream". In that example, p and q are both false and "if p then q" comes out true. Some people think that we should have a "relevance logic" in which the truth-value of the sentence "if p then q" is not solely a function of the truth-values of p and q. However, in that logic it will still be the case that if p is true and q is false then "if p then q" will come out false. Which is enough for the argument I gave to come out deductively valid. As I was trying to explain before. So it does not matter if you interpret the "if... then" connective in the sense of relevance logic, the argument will still come out deductively valid. When you say "why do you give a different definition", which definition of mine do you have in mind? Are you talking about my definition of subjectivism or my definition of error theory?
When you say "why do you give a different definition", which definition of mine do you have in mind? Are you talking about my definition of subjectivism or my definition of error theory?Subjectivism
When you say "why do you give a different definition", which definition of mine do you have in mind? Are you talking about my definition of subjectivism or my definition of error theory?Subjectivism So you're asking why did I give a different definition to the one in the Wikipedia article? The answer is, because I wanted to remain true to what Peter Singer seemed to mean by "subjectivism" in the lectures for the on-line course. And the argument I presented was "an existing argument" in the sense that it could be seen as implicit in some remarks that Peter Singer made during the lectures.