Why is this argument valid? Velleman

Question

Why is the pictured argument valid?

Velleman in this chapter section says that an argument is valid only if the conclusion has the option of not being true if all the premises are true.

But row 7 is the only row where all three premises (Premise 1 - "P1", Premise 2 - "P2" and Premise 3 - "P3") are true yet the conclusion (last column "C" or "P") is false.

This shows the argument is invalid. I'm not sure why Velleman has this as valid?

Not sure. That's really weird. I remember doing Velleman back in the day, but don't remember this. — Rushabh Mehta, Apr 18 '19 at 00:27

score 1 · Answer 1 · answered Apr 18 '19 at 00:34

1

The argument is valid, no matter how you look at it.

The mistake is where it writes "Pete win Chemstry price is represented by P".

Actually, you will see it is represented by C before, and if you copy the colunm C, nothing weird happens.

answered Apr 18 '19 at 00:34

StAKmod

1,338

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What does this say? I'm not able to understand. – Rushabh Mehta Apr 18 '19 at 01:20
@StAkmod, thanks! I see what you are saying regarding the mistake! Indeed they have mixed up P with C. But you also appear to be saying in your first sentence that the argument would still be valid even with the mix-up. How could this be? Line 7 as is would still show T for the premises and F for the conclusion. – user152810 Apr 18 '19 at 02:21

Why is this argument valid? Velleman

1 Answers1