What exactly makes a class difficult?

Is it a professor with indecipherable handwriting who mumbles through lectures and refuses to curve a test with a 47% average score? Is it hours upon hours of complex proofs or twelve-page research papers covering abstract concepts?

There's no exact science for makes a class tough. It's all subjective, to a point - what's a breeze for one student might be painful for another. But what we do know is that fighting through a semester with a truly difficult class is a rite of passage in college. The academics are supposedly why we're all here, after all, and you can't earn that diploma without putting in a little blood, sweat and tears. We can all relate to that one class that makes us feel like maybe dropping out and working at the local car wash wouldn't be the worst idea ever.

1. Thermodynamics II--Purdue University

If you're looking for courses to boost your GPA, signing up for a course in Thermodynamics (the science of heat transfer) is probably not the way to go. "At Purdue, the engineering courses are notorious for being particularly hard," says Amanda, a sophomore at Purdue. "Because Purdue is known for its engineering program, the standards for getting into the program are extremely difficult and the 'weed-out' courses are especially difficult." But engineering students beware: even if you've made it through Thermodynamics I, don't expect to find any relief in the next level. On MyEdu.com, the workload for Thermodynamics II is ranked as "heavy" and the official grade record shows 50% of the class received a C or lower (4% Fs and only 17% As.)

2. Topics in Metaphysics and Epistemology--New York University

If you're partial to numbers and concrete answers, this class will send you running in the opposite direction: "the nature of cause and the existence of universals" and "the distinction between appearance and reality" are just a couple of the topics tackled in this advanced philosophy course. "I definitely wouldn't recommend this class to anyone who isn't comfortable with basic philosophic thinking and looking for a challenge intellectually," says Erin, a senior at NYU who took the class last year. With this course, NYU's top-ranked philosophy department proves that difficult classes are definitely not limited to the fields of math and science.