Several great ideas have to be understood, in order to grasp properly the workings of the Vedanta philosophy. In the first place it is not philosophy in the sense we speak of the philosophy of Kant and Hegel. It is not one book, or the work of one man. Vedanta is the name of a series of books written at different times. Sometimes in one of these productions there will be fifty different things. Neither are they properly arranged; the thoughts, as it were, have been jotted down. 

Sometimes in the midst of other extraneous things, we find some wonderful idea. But one fact is remarkable, that these ideas in the Upanishads would be always progressing. In that crude old language, the working of the mind of every one of the sages has been, as it were, painted just as it went; how the ideas are at first very crude, and they become finer and finer till they reach the goal of the Vedanta, and this goal assumes a philosophical name.

 Just at first it was a search after the Devas, the bright ones, and then it was the origin of the universe, and the very same search is getting another name, more philosophical, clearer — the unity of all things — "Knowing which everything else becomes known."

Swami Vivekananda