The personified Vedas stated that persons born after the creation of this material world cannot understand the existence of the Supreme Personality of Godhead by manipulating their material knowledge. Just as a person born in a particular family cannot understand the position of his great-grandfather, who lived before the birth of the recent generation, we are unable to understand the Supreme Personality of Godhead, Nārāyaṇa, or Kṛṣṇa, who exists eternally in the spiritual world. In the Eighth Chapter of the Bhagavad-gītā it is clearly said that the Supreme Person, who lives eternally in the spiritual kingdom of God (sanātana-dhāma), can be approached only by devotional service.
As for the material creation, Brahmā is the first created person. Before Brahmā there was no living creature within this material world; it was void and dark until Brahmā was born on the lotus flower that sprouted from the abdomen of Garbhodakaśāyī Viṣṇu. Garbhodakaśāyī Viṣṇu is an expansion of Kāraṇodakaśāyī Viṣṇu, Kāraṇodakaśāyī Viṣṇu is an expansion of Saṅkarṣaṇa, and Saṅkarṣaṇa is an expansion of Balarāma, who is an immediate expansion of Lord Kṛṣṇa. After the creation of Brahmā, the two kinds of demigods were born: demigods like the four brothers Sanaka, Sanātana, Sanandana and Sanat-kumāra, who are representatives of renunciation of the world, and demigods like Marīci and their descendants, who are meant to enjoy this material world. From these two kinds of demigods were gradually manifested all other living entities, including the human beings. Thus all living creatures within this material world, including Brahmā, all the demigods and all the Rākṣasas, are to be considered modern. This means that they were all born recently. Therefore, just as a person born recently in a family cannot understand the situation of his distant forefather, no one within this material world can understand the position of the Supreme Lord in the spiritual world, because the material world has only recently been created. Although they have a long duration of existence, all the manifestations of the material world—namely the time element, the living entities, the Vedas and the gross and subtle material elements—are created at some point. Thus any process manufactured within this created situation as a means for understanding the original source of creation is to be considered modern.
Therefore by the process of self-realization or God realization through fruitive activities, philosophical speculation or mystic yoga, one cannot actually approach the supreme source of everything. When the creation is completely terminated—when there is no existence of the Vedas, no existence of material time, and no existence of the gross and subtle material elements, and when all the living entities are in the nonmanifested stage, resting within Nārāyaṇa—then all these manufactured processes become null and void and cannot act. Devotional service, however, is eternally going on in the eternal spiritual world. Therefore the only factual process of self-realization or God realization is devotional service, and one who takes to this process takes to the real process of God realization.
In this regard, Śrīla Śrīdhara Svāmī has composed a verse which conveys the idea that the supreme source of everything, the Supreme Personality of Godhead, is so great and unlimited that it is not possible for the living entity to understand Him by any material acquisition. One should therefore pray to the Lord to be engaged in His devotional service eternally, so that by the grace of the Lord one can understand the supreme source of creation. The supreme source of creation, the Supreme Lord, reveals Himself only to the devotees. In the Fourth Chapter of the Bhagavad-gītā the Lord says to Arjuna, “My dear Arjuna, because you are My devotee and because you are My intimate friend, I shall reveal to you the process of understanding Me.” In other words, the supreme source of creation, the Supreme Personality of Godhead, cannot be understood by our own endeavor. We have to please Him with devotional service, and then He will reveal Himself to us. Then we can understand Him to some extent.