My alma mater required engineering students to take a reasonable amount of credits in something other than engineering. Enough to be close to a minor, but more flexible.

I always thought this was an excellent idea.

Isn't a philosophy/CS double major kind of like a math/CS double major? In that it expands your knowledge in the same domain, rather than a completely new one would (like, for example, studying German literature or biology would).

I remember helping my sister with her philosophy home work, and being surprised by the amount of elementary logic and set theory being taught.

That depends in large part on the philosophy department. More analytic [1] departments will teach lots of courses that could just as well be cross-listed as theoretical computer science courses.

But some departments are less analytic (e.g. departments heavy on [2] and [3] aren't too difficult to find in the US). In those departments, the mode of thinking is very different from what you'll experience in a CS course.

And in both cases, taking a lot of humanity courses will teach you how to write well. Which is definitely a skill that a lot of CS majors lack.

(Also, a course of study in analytic philosophy can definitely help round out a CS major that's too light on the theory courses.)

[1] https://en.wikipedia.org/wiki/Analytic_philosophy

[2] https://en.wikipedia.org/wiki/Continental_philosophy

[3] https://en.wikipedia.org/wiki/Classics

Other than a class on logic, all of my other courses involved enormous amount of written argumentation, e.g., reasoning, ancient philosophy, modern philosophy, Asian philosophy, philosophy of mind, philosophy of science, philosophy of film, metaphysics, etc. I would say that only logic had a direction connection to computer science, although as a computer scientist, I would choose to write essays about the Turing test, philosophy of AI, etc. This was 15+ years ago, but I assume things are still the same in many philosophy departments.

I wouldn't say either of those expand your knowledge in the same domain. Related, sure.

In Australia we have the ability to do a double degree not just a double major.

It usually saves 2 years compared to doing them separately and you get 2 degrees on the final piece of testament.

I found it tremendously useful as my "humanity" was my Physics degree to complement the Comp Sci. Plenty of philosophy in the hard sciences when you learn the history and where we are going.