Error (?) at page 69-70: Chapter 2.3, Exercise 9

[MetallicCrimson]

The argument is indeed invalid; but in the truth table, shouldn't the 2nd, 3rd and 4th rows be blue (critical) instead of the 1st, 3rd and 4th rows?
p ∧ q → ∼ r is false in the first row (T, T, T), so that's not a critical row. But it's true in the second row (T, T, F), so it is a critical row, which also has a true conclusion, so that row doesn't make the argument invalid.
(The third line does it anyways.)

[spamegg1]

Oh yeah... first and second row results need to be switched there.
Good catch, thanks!

[spamegg1]

Closed by #44 thanks a lot!