From Bhagavad-gītā we must learn what God is, what the living entities are, what prakṛti is, what the cosmic manifestation is, how it is controlled by time, and what the activities of the living entities are.
Out of these five basic subject matters in Bhagavad-gītā it is established that the Supreme Godhead, or Kṛṣṇa, or Brahman, or the supreme controller, or Paramātmā—you may use whatever name you like—is the greatest of all. The living beings are in quality like the supreme controller. For instance, the Lord has control over the universal affairs of material nature, as will be explained in the later chapters of Bhagavad-gītā. Material nature is not independent. She is acting under the directions of the Supreme Lord. As Lord Kṛṣṇa says, mayādhyakṣeṇa prakṛtiḥ sūyate sa-carācaram: "This material nature is working under My direction." When we see wonderful things happening in the cosmic nature, we should know that behind this cosmic manifestation there is a controller.