Philosophy (Logic) I was reading my daily reddit and came accross this link to a new double major at Oxford, Computer Science and Philosophy.
https://www.ox.ac.uk/admissions/undergraduate/courses-listing/computer-science-and-philosophy
I just wish my university had a double major like this, i would have taken it as an undergrad for sure (I am now doing graduate research in CS). Anyways, i wanted to ask what books are good for beginning and intermediate levels in Logic. I know theres like Deductive Logic, Set Theory, but the actual books i don't know any.
 A: My preferred intro logic text is Enderton's "A mathematical introduction to logic." Smullyan's book on first-order logic is very nice, though it uses proof trees, which is (awesome but) somewhat unusual. I'm also a fan of Peter Smith's "An Introduction to Godel's Theorems." As far as set theory goes, it really depends how far you'd like to go. I imagine that if you're doing graduate research in CS you know the "basics" that would be covered in Halmos' "Naive Set Theory." If you're looking for more, I also like Enderton's "Set Theory," and after that a big standard text is Jech's. 
There's obviously more. You need a good textbook for modal logic, and I don't know any. Hopefully someone else can help fill in the picture.
A: Lectures in Logic and Set Theory (Volumes 1 and 2) by George Tourlakis. This is (in my opinion) a good beginner-intermediate book. I flipped through both volumes and liked the writing style and presentation. It's not too verbose or too terse.
A: I second the recommendations for Enderton's texts: Both "A mathematical introduction  to logic" and his text on set theory.  If you want something to peruse right now, Paul Teller has a fairly good introduction to logic, available on-line (free, no strings attached)
here or, more directly, there.
The first volume is pretty elementary, but the second gets slightly more complex.  It's a good start, depending on your background in logic. 
Another "starter" book, a bit more rigorous than the usual "Intro to Logic" text, is the classic by Benson Mates, "Elementary Logic", 2nd edition.  It's not nearly as "elementary" as some introductory texts, and would be a great start if you're just getting your "feet wet".
A: My first suggestion would be the following article:

Samuel R. Buss, Alexander S. Kechris, Anand Pillay & Richard A. Shore, The Prospects for Mathematical Logic in the Twenty-First Century, 2001, Bulletin of Symbolic Logic 7 (2):169-196.

As a second suggestion, I would suggest reading the articles on Stanford Encyclopedia of Philosophy, the quality is wonderful. Each article is written by an expert on the topic. If you want to know more about a topic, check the list of references at the button of the article.
ps:
Berkley and CMU also have quite good programs at the intersection of logic and philosophy, and you can find similar programs by Googling.
A: So this isn't the logic reference you asked for, but if you are interested in Philosophy and Computer Science, you might want to check out this website for an MIT course run by Scott Aaronson called "Philosophy and Theoretical Computer Science"
https://stellar.mit.edu/S/course/6/fa11/6.893/index.html
It is a good collection of papers and other references, including a paper of Scott's called "Why Philosophers Should Care About Computational Complexity" that is pretty interesting.
