This should only be allowed if a student has written a more extensive paper on a topic covered in two courses. E.g. if a student is taking a course in moral philosophy and another in epistemology, and the standard length is 10 to 12 pages, then, if both professors agree, it would be acceptable to submit one 20 to 24 page paper on moral epistemology for both courses. In other words, submitting the same paper should not be used as a way of getting away with doing less work.
This should only be allowed if a student has written a more extensive paper on a topic covered in two courses. E.g. if a student is taking a course in moral philosophy and another in epistemology, and the standard length is 10 to 12 pages, then, if both professors agree, it would be acceptable to submit one 20 to 24 page paper on moral epistemology for both courses. In other words, submitting the same paper should not be used as a way of getting away with doing less work.
I do not mind at all when students in a doctoral program use parts of their papers from classes to build upon their literature review for their dissertation. This just seems like smart planning to me. I usually advise my students to choose paper topics in their classes that may later be used in their dissertation. I would feel similarly about students using parts of their papers from classes in their Master's Thesis.