<p>"So yea, please enlighten me as to why calculus 1,2,3 and diff eq are generally prerequisites for higher-level math. "</p>
<p>feurfollets, what math I have taken has nothing to do with the my answer. However, since you want to be enlightened, please feel free to read the math prerequisites for upper level math classes at Penn. For example, Complex analysis requires calc 3 as a prereq and diff eq is part of the course description for calc 3 at Penn. If you want to discuss what you need to know to do real analysis (some of which I had to learn in some advanced economics classes) or topology (I wrote a paper on topology 100 years ago when I was in high school before i took calculus), I think you make some valid points. However, I wanted to point out to the OP that there are prerequisites that a univeristy will require before s/he can enroll in those classes.</p>