Although human knowledge contains tens of thousands of broad subjects, they can be simply divided into two categories: nature and humanities. All phenomenon in the world also belong to these two categories. Nature refers to everything outside of the human race whereas humanities are all about the human society itself. Of course, human beings are part of the nature cycles, but we as humans should focus on the role of our own life. Thus, it follows the rules of nature that we divide our knowledge into nature and humanities.
Because of the difference between nature and humanities, we have different ways of learning these two kinds of knowledge.