The Bhagavad-gita is a narrative spoken by Sanjaya, the secretary of Maharaja Dhrtarastra. This is just like airwaves from the radio: the play is going on in the auditorium, but you can hear from your room. So, just as we now have such a mechanical arrangement, at that time there were also certain arrangements, although there was no machine. Anyway, the secretary of Dhrtarastra could see what was going on in the battlefield, and he was in the palace, telling this to Maharaja Dhrtarastra, who was blind. Now, the conclusion made by Sanjaya was that Krishna is the Supreme Personality of Godhead.