Btw, I was agreeing with KappaMD and referring to Angel's post.
agzg, I agree. Intro level courses across disciplines** are designed to reach a range of students. Therefore, the textbooks are more cut and dry. Professors sometimes try to challenge intro students to think beyond the cut and dry, but that's only successful for the "good students" who know how to do more than memorize information. Upper level courses across disciplines are still concrete to a great extent (we'd be debating students' grades all day if there was never a clear right or wrong), but go beyond the "concrete" and therefore have more leniency (both good and bad) on the part of the professors.
**social sciences, math, and science