Quote:There seems to be some consistency that suggests that perplexed might be better used where doubt is caused by something that is inherently intricate but not necessarily disorderly--such as differential calculus.
Given the variation of ad hoc methods available for solving differential calculus by hand, one might argue that it is not such a well-ordered problem...but your point is clear.
However, even a well ordered problem can cause an equally high degree of disorder to one's thoughts, hence the statement "I am confused," not "this problem is confused." We say "this problem is confusing," but that only means that the problem leads to confusion of the reader's thoughts, which does not imply that the problem itself is disordered (although that may well be the case).
Since both of these conditions are used to describe a person's state of mind, and since both ordered and disordered problems may lead to disordered states of mind, I do not see a difference.