Mathematics is probably what I've studied most, especially set theory. If I had to sum up my knowledge of mathematics I'd say I knew basic calc, a lot of set theory, and smatterings of everything else. My knowledge in natural science is limited. My current quest is learn as much physics as I can while refusing to accept any scientific knowledge unless I've seen and fully understood the experiments or evidence supporting it. So far this quest is taking me mostly into a study of the history of science, which is one of my favorite topics.