haggholm | When debate fails (Reply)

It’s a sad and extremely frustrating thing when someone mistakenly thinks that they understand logic. Never mind the context or subject matter; suffice to say that I was addressing the logical form of an argument (which was invalid—the argument was begging the question) whereas this individual thought that I was addressing the issue as a whole, in spite of my repeatedly telling him that I was talking about the strict logic.

The problem turned out to be that he had no idea what strict logic really is. The following is a lightly trimmed and reformatted (but not otherwise edited) extract of part of the discussion.

I really find it difficult to follow what you consider to be valid logic.

http://www.iep.utm.edu/v/val-snd.htm will give you a primer. Read and digest.

I read your primer for about two seconds and I found this.

"A deductive argument is sound if and only if it is both valid, and all of its premises are actually true. Otherwise, a deductive argument is unsound."

I disagree. I'd say that the soundness of an argument is a measure of its deductive validity.

Then you have no idea what you are talking about. "Sound" is a technical term in formal logic, not subject to debate or interpretation. You may as well say that you think that the equivalence of two additive expressions is a measure of its approximate satisfaction of your requirements -- it's nonsense; "soundness" and "equivalence" are formal terms (in logic and mathematics, respectively) with very precise definitions.

If the premises are true and the deduction is valid then that makes the deduction also true, doesn't it. A sound argument only needs to have relevant premises and valid reasoning, in my opinion.

You don't get to inject your own opinion of the meaning of "sound", "valid", "plus", "minus", or "equals". If we are speaking of logic, you may safely assume that we are using the terminology of logic.

An argument therefore would be sound if it addressed a problem and came up with a reasonable and relevant solution. Since we don't always know whether premises are actually true when we use them in deductive logic, we need a general adjective which indicates that the logical processes of an argument have been correctly folowed, and I'd say that adjective could be "sound". So generally, "soundness" refers to the reasoning processes and not to the truth of the premises, which could always be in doubt.

Also there is a comma, placed incorrectly before the word "and". What's more, unless the word "actually" is supposed to indicate an element of surprise, it's redundant.

So I don't think I'll read your logic primer further, thankyou. I don't think I need it.

Clearly not…