"So Krishna, or the Supreme Lord, is always anxious to revive the memory of these forgotten souls, conditioned souls. Now, how He revives? He revives in sastra. Sastra means scripture. Sastra, guru, spiritual master. Sastra, guru, atma-rupe. And sometimes He comes Himself or as Paramatma, or the Supersoul. He is giving you instruction from within as Paramatma, He's sending you suitable spiritual master so can, you can have instruction without, and the books are, the scriptures are there. So many facilities the Lord has created. And therefore the human form of life is meant for utilizing all these facilities. In the animal form of life there is no facility. They cannot read sastra. They cannot understand scripture. They cannot take the advantage of a bona fide spiritual master. They cannot consult within with God. They have no this capacity. Their consciousness is so undeveloped that it is not possible to have, utilize all these facilities. But in human form of life we can utilize all these facilities. The sastras are there, the Vedas are there, scriptures are there. And still, although it is the age of Kali, still, those who are following the disciplic succession, there is bona fide spiritual master also. Sastra, guru and atma. And over all, the Paramatma. The Paramatma, the Supersoul, Krishna as Supersoul, is sitting within your heart along with you. And as soon as, by the instruction of the scripture and direction of the spiritual master, you begin sincerely something, the Paramatma, from within you, He'll speak, 'Yes, now you are right.' He'll speak to you."
(Srila Prabhupada lecture, New York, November 25, 1966)