A colleague told me his view of learning. You start from zero and learn something. At some point you might get the feeling that you know everything. You then learn more, and if you go on to graduate level studies, you might end up feeling that you know nothing! Then, he said, you might really know a little bit about something very small.
In some sense, he’s right. On the graduate level, one learns ‘cutting-edge’ science or at least one gets some perspective of the entire body of knowledge on ones field. Intrinsic in this process one also learns what the existing body of knowledge and the current scientific regime cannot explain. Typically, scientific discoveries opens up more questions than are answered, particularly in scientific revolutions. From the cutting-edge-of-science perspective one sees a vast range of problems and unanswered questions. Ones knowledge, however, certainly is limited. It is true, then, that one does not necessarily know very much about many different things, but one has to know quite a lot about some things.