He showed by practical example. He is accepted by great, great sages like Nārada, Vyāsadeva, Devala, Asita. That is also stated when Arjuna accept Him that "You are the Supreme Lord. So You are the Supreme Lord how? Because people may say I am Your friend, therefore I am accepting. No. All the authorities says that You are the Supreme Lord. And I have understood by Your personal explanation, and I accept You." Sarvam etad ṛtaṁ manye yad vadasi keśava (BG 10.14): "Whatever You have said, I accept it because You are Bhagavān." This is Bhagavān.
So if you accept Bhagavān's word with firm conviction, then your life is perfect immediately. Immediately you become perfect. There is no difficulty. Because I may be imperfect, but if I say that "I have understood this is, this glass, this spectacle is spectacle. I have learned it from authority," that is a fact. I may be imperfect, but because I have learned from authorities that "This is a spectacle. This is called spectacle," then this statement is correct. Similarly, we may be imperfect, it doesn't matter, but because we are accepting the words and statement of Kṛṣṇa, then our knowledge is imperfect . . . perfect. It is not imperfect.