Before I studied philosophy, I studied math. I was working on a PhD in set theory when I became less interested in how-do-you-prove-the-theorem and more interested in questions like what-does-it-mean-if-you-can't-prove-or-disprove-the-theorem?
Among other things, this means that before I started studying philosophy I spent a certain amount of time teaching mathematics. I started as a teaching assistant for introductory courses like Calculus and Statistics, and then I was a teaching assistant for more advanced courses like Differential Equations, and then toward the end I taught a few classes myself, including one on how to do mathematical proofs.
Math is hard. But I found teaching mathematics to be mostly straightforward and rewarding. Students are usually externally motivated to learn: they want to do physics, or engineering, or more advanced math, or whatever, and to do it they have to learn some math. Except in the case of bogus requirements -- like baby calculus for no reason for majors like business to "weed out" students they didn't like -- the importance and relevance of the subject was relatively obvious.
At the level of undergraduate teaching at least, math is also coherent and unchanging. Because of the nature of the subject, the same kinds of things confuse people, and similar kinds of questions arise again and again. Once I had explained concepts like limits, differentiation, and integration a few times, the ideas were cemented in my head in such a way that very little teaching preparation was required.
On top of everything else, because math is obviously difficult, a teacher's ability to break down difficult concepts to make them seem simple earns them great respect. And this was something I was relatively good at.
Several years into the process of studying for a PhD in math I switched to philosophy. I've now been teaching philosophy in one form or another for ... well, a lot of years. And my personal opinion is that teaching philosophy is way more difficult and way more time-consuming than teaching mathematics. I don't have a lot of experience with the other humanities, but it is my belief that the reasons apply to humanities teaching generally.
Those reasons are several. For one thing, math seems difficult and a teacher is there to make it seem simpler, but in the humanities, it's often necessary to start by taking something that seems simple and showing students how difficult it is. I teach ethics, and philosophy of sex and love, and contemporary moral problems, and philosophy of economics. In all of these areas there's a sense in which a student already knows what they think about things, and part of my job is to complicate that -- to raise questions about things that seem obvious, to showcase views that seem counter-intuitive, and to just generally show how many different factors and perspectives can come into play.
This is intellectually difficult, and it can also be emotionally draining. How do you frame the issues when students are coming into the room with very different background assumptions - and you don't even know what those background assumptions are? How do you encourage people to speak up when part of your job is to suggest they might be totally wrong? How, exactly, do you figure out the line between constructively challenging existing beliefs and just being a contrarian pain in the ass?
Some people love the way humanities thinking challenges them, but other people find it exhausting and annoying. Sometimes science students in my ethical thinking class tell me how frustrated they are by the lack of a "right answer" in philosophy. I sympathize! It can be frustrating as hell. Unfortunately, the problems we're talking about are the ones that don't have straightforward answers, so it's the best we can do to muddle through.
Another factor, of course, is the variation and unpredictability of what kinds of things are going to come up. The social and cultural world we're living in makes different things seem obvious in different times. Even just contingently there are classrooms where one thing seems really important that didn't seem important to some other group.
This variation and unpredictability is, of course, part of what makes humanities teaching so important, relevant, engaging, and fun. But it also means that while teaching an interactive mathematics class can feel like a going through a play you're performed a thousand times, teaching an interactive humanities class can feel like a high-wire act where the tricks are constantly changing.
And finally, of course, there's grading. While mathematics grading can be time-consuming (when I did it, we didn't just grade yes-or-no, we looked at student work for partial credit) it's not like grading a paper -- work that combines engaging with someone's novel ideas and helping them toward an amorphous goal like "writing well." As we've discussed before, it takes a lot of time and energy, and it's not something you can scale up.
A few times recently I happened to be in large university group settings, where people were coming from a range of disciplines. And in that context, I heard some remarks about how, from the point of view of the sciences, what we humanities might regard as a large-ish class -- like, 50 or 100 students -- is to them a very small class. No one said it, but I felt the suggestion that somehow we humanities people weren't pulling our weight, that what we were doing was some kind of niche thing, cute and nice if you can afford it, but not really where the action is.
And I can't really say, because I have no experience teaching science. I only taught math -- which to me is a completely different kettle of fish. But from my perspective, the time and energy to teach a philosophy class is way more than the time and energy of teaching a mathematics class. Even when the classes are a lot smaller.
None of this is meant as a complaint. I love university students, and I love being around them. I think the people who criticize the younger generation for being phone-obsessed and jobless are wrong and ill-informed, and that today's young people are the hope of the future. I regard helping these young people understand the complex world around them as one of the best things anyone can do.
I'm just saying: for me, anyway, teaching about utilitarianism is way harder than teaching what it means to take the limit as h goes to zero.