Thus is revealed to you by Me, this greatest secret of all śāstras, O sinless soul. Understanding this, O Bhārata, does one become wise and fulfilled.
Krishna says he has revealed to Arjuna the entire secret contained in all śāstras. Śāstra is a rational, systematic presentation of its subject, evaluating the good and the bad, the merits and the demerits of what it exposes. Strength and purpose of the śāstras consist in enlightening the reader or listener.
Krishna has covered the entire complex nature, display of which is the endless Creation. He has also revealed that the measure and magnitude the senses reveal have their locus within one’s own body, in the mind and the intelligence.
Outwardness and grossness are but notional. A proper knowledge about this will show that the mind within is the sole source of every experience and expression. This, in turn, leads to the subsidence of desires, hatred and fear, making the seeker free, natural and harmonious. One becomes an all-worshipper, his worship including all his attitudes and goals alike. With the dawning of wisdom he fulfils the purpose of life.