Well, like you said, you were given 5 possible topics. These likely covered,together, a large amount of the course material that you need to know. With an in-class essay, you are forced to learn all of the material so that you will be able to answer on any of the topics. An in-class essay on an exam is not just equivalent to an assigned paper; they both test your ability to evaluate and analyze a situation/topic/whatever and to create cognizant arguments, but in a paper the teacher will be much more critical about the formatting and they will expect deeper, more well supported arguments, because those are also skills they are evaluating(ability to research, ability to write a properly formatted paper). In-class papers are usually very lax in those categories because it is about content knowledge, but it is in an essay format because that allows them to test higher-order thinking. http://ww2.odu.edu/educ/roverbau/Bloom/fx_Bloom_New.jpg This is bloom's taxonomy, where you can see that an in-class essay gives the learners a chance to evaluate, analyze, etc, better than say, multiple choice questions that work better for testing remembering, understanding, and other lower-order thinking