Would you pass an introductory logic class? | Comments

The explanation for number 4 states:

"An argument is valid if it is impossible for the premises to be true and the conclusion false. It is impossible for a contradiction to be true, so any conclusion goes."

Let's break this argument down, shall we?
A = An argument is valid.
P = Premises are true.
C = Conclusion is true.
The explanation could then be rewritten as
If A then not (P and not C)
not P
Therefore C

How in the world do you get C from that? You can't. You could have not C and all your premises would still be true.

It's absolutely nonsensical. You can't get a valid conclusion unless you have a valid argument.

Otherwise I could make up nonsensical invalid argument, stick any conclusion on the end and claim the conclusion is valid. Would would be the point of logic if that were the case?

TLDR; If you answered 4 with "none of the above" you were right, the author was wrong.

Here's a little logic for you:

"A conclusion if valid, if and only if it has a valid argument to support it.

'Elivs is alive and Elvis is not alive' is not a valid argument.

Therefore any conclusion you derive from the premises 'Elvis is alive and Elvis is not alive' is invalid.'"

If you are trying to learn logic, I recommend you don't believe their explanation for that particular problem.

In all fairness, on the comment below, I messed up the first line in the translation:

The argument should read
If not (not P and C) then A
not P
Therefore C

It's still not a valid argument. But, it was sloppy interpretation on my part.

I got 50% too and I'm taking a logic class in college right now.

I am 50% able to pass lol :P