Harry Lewis once said to me "Flip through the course catalog, write down the 32 courses you most want to take, and then figure out which concentration requires the fewest changes to what you've written down. Then pick that one."

As it turns out, I had many CS courses, several math courses, and was planning to write a thesis (most likely on the math-y edge of CS theory). So CS/Math was a perfect fit. (Math/CS is strictly more required courses, and requires approximately the same writing commitments.) But basically, it feels like I've turned in a piece of paper that convinced the admin that the thing that I was going to do anyway, is well-aligned with their expectations for academic rigor. It's no big deal.The real question, I suppose, is then: "What is it like to study Math and CS at Harvard?"

In general, and in a word, exhausting. Your fellow students are excellent, and if you have a day when you feel like you're not, it can get pretty miserable. It gets better when you realize that everyone is best at some subset of fields, and if you're lucky, you'll find the particular subset that you do well at, and can be proud of that.

Along the way, you make friends (you have to, to survive!) and when the same people start cropping up in your classes repeatedly, you realize that they're in it for the long haul, too, and start to form a friendship forged in mutual suffering. It's pretty great. But then again, most of them are likely only-math, or only-CS, or math-physics, or something, so they end up in one part of your life and not the other (and even if they're better at the thing that you share, you're often better at your 'other half'). So you've got different groups of friends, and it can feel like you're living two different lives, I suppose. (More, if you've got another significant field of study...)

As far as teaching, all of my professors so far have been superb. In particular,

• David Malan (CS 50)
• Margo Seltzer (CS 161, 261)
• Benedict Gross (Math 25a, 25b)
• Jacob Lurie (Math 114)
• Curtis McMullen (Math 131)

are all professors who I would recommend wholeheartedly.

As far as material, I can only really speak to Math (and maybe the Systems subfield of CS). In the former, the breadth of material required, even of a joint concentrator, does a great job of exposing you to different mathematical structures and patterns of thought, and reading between the lines gives you a real sense of what 'math' truly is. As far as Systems goes, well, all I can say is that Prof. Seltzer is a fantastic lecturer and an absolute genius, and that she's given me enormous insight into the technical atoms out of which modern computation is built.

By way of summary, I'll once again echo Prof. Lewis's advice. If you were going to take all (or most) of the classes anyway, then go ahead and declare (or switch!) CS/Math. If it'd force you to take many classes you didn't want to anyway, it's probably not for you. (Not judgmental, just a fact.) But for me, it's the right choice, and I'm enjoying it immensely.