Mathematical logic is a very interesting topic. However this class doesn't really do it justice. The main issue I have is that the class has a prerequisite of Math 131A OR 110A OR philosophy 135. The problem lies in the OR.

If you have never taken any logic class before (not even philosophy 31) you will have a very hard time in this class. The first two weeks you as a math major will find the class easy since it's pretty obvious induction proofs on syntax and semantics. Then comes week 3 when you are introduced to formal deduction and you hit a wall. You have never even heard of basic inference rules like implication introduction/elimination/distribution in basic propositional logic; yet you are supposed to do reasoning on a richer language (first-order logic) using just two rules of inference (implication elimination and a "quantifier rule" that isn't valid). And things go downhill from here. Of course I later understood the reason why we use such a small number of rules later on: it's for making proofs ABOUT logic easier but not making proofs WITHIN this language easier; duh!

Eventually I did find this class pretty interesting, especially later parts with a little bit of computability theory (like primitive recursive functions). But that's after weeks of struggling with formal deduction that you really should have had some foundations for.

My advice is that don't take this class unless you've taken logic classes before. Philosophy 31 is a cool class and maybe take that class before this one. Better yet you know take philosophy 135 which is a prerequisite. At least read through the whole Stanford introduction to logic beforehand or you'll be utterly lost come week 3.

I should also mention that Professor Martin is pretty old and frequently makes typos. He's also not particularly good at explaining himself. I really hope that instead of him, Professor Moschovakis can teach this class as he did in 2017. Professor Martin and Professor Moschovakis's notes are completely different it feels like they are teaching a different course.