Page 18 “Theorem 3. If $\models A$ and $\models A\to B$, then $\models B$.”
Page 43 From prove of Theorem 12. “By Theorem 3, given that premises $A$ and $B$ for an application of modus ponens are valid, so is the conclusion $B$.”
It is looks to me as misprint. It should be “By Theorem 3, given that premises $A$ and $A\to B$ for an application of modus ponens are valid, so is the conclusion $B$.”
Am I right?
In order not to leave this question unanswered, I will turn my earlier comment into an answer.
Yes, you are right, it definitely should be $A\to B$, and not simply $B$. Minor slip.
Luckily, Google books gave a generous preview, so I was able to see the entire context: there is no doubt.
Dover does not seem to maintain an errata file, and there is nothing on the web site of the original publisher (Wiley).
