Man has a double nature as described in the Gita. His true nature is what he has brought down from his true home, the Home of Bliss. But this true nature is covered up with another nature that has evolved and is still evolving through the circuits of mind and life and body, from the plant and animal to human existence. The desire to discover true happiness and freedom and love springs from his own deeper self. To discover it he has to go behind his surface nature as it stands today and find the secret soul. To live in his soul would give him the happiness he seeks.