It is human nature as such that is displayed in the dramas of Shakespeare, the epics of Homer or the Mahabharata. It is not the story of some people that lived sometime ago but a characterization of all people that may live at any time in the history of the world. The characters are perpetual features in the evolution of the cosmos, while the vehicles which embody or enshrine these characters may vary. These are the specific stages through which the world has to pass, and every individual is a part of the world. Everyone has to traverse every one of these stages.
Every character is every person and vice-versa.
Thus, while the epic of the Mahabharata, like some other epics also of this nature, attempts to portray the culture of an entire nation, or, we may say, the culture of humanity in general, it pinpoints its teachings at a central occasion which it regards as the most convenient hour to give its message in its essentiality. The Bhagavadgita is the kernel of this vast expanded fruit of the Mahabharata, which has matured out of the tree of the culture of India. The philosophic messages which are given in the various chapters of the Gita are dramatically portrayed in the characters of the story of the epic. The one explains the other. The great author of this epic achieves a double stroke by his masterpiece that he has given to mankind.