Those who are grossly materialistic, those who do not know that beyond this materialistic body there is the soul, they cannot understand, for them, this yogic principle is recommended, to exercise this body. As if by exercising the body he will understand God and understand religion.
Therefore the yoga system is not recommended for the first-class men. First-class men, they know that by gymnastic process of exercising the material senses, one can(not) understand God or religion. Viśuddham. It is beyond.
Therefore another name of Kṛṣṇa, or God, is Adhokṣaja. Adhaḥ. Adhaḥ means falls down, and akṣaja, akṣaja means . . . akṣa means direct experience, direct seeing, direct touching. And ja means born. Knowledge born of direct perception of the senses—this is called akṣaja. And adhaḥ means where akṣaja, the direct perception of material senses, is cut down. There is no possibility. He is called adhokṣaja. Therefore, Kṛṣṇa's another name is Adhokṣaja: "beyond the sense perception knowledge."
Panthās tu koṭi-śata-vatsara-sampragamyaḥ. We cannot understand God or religion by our mental speculation even by the speed of mind, manasā. Panthās tu koṭi-śata-vatsara. And the speculation continues by . . . continues to hundreds and hundreds of years. Panthās tu koṭi-śata-vatsara. Śata means hundred, and koṭi means ten million. So ten million into hundred—then unlimited time. If you go on speculating, by speculation, panthās tu koṭi, still, your conception of God or religion will remain incomplete.
Panthās tu koṭi-śata-vatsara-sampragamyo vāyor athāpi (Bs. 5.34). By airplane, with the speed of the mind . . . there are different airplanes, and they have got different speeds. Now, if you manufacture an airplane which runs with the speed of the mind . . . you know the speed of the mind. Within a second, you can travel millions of miles.
So an airplane running on, on that speed, and thinking for millions of years, still, you cannot approach the abode of Kṛṣṇa or understand Kṛṣṇa. Only you can understand by His mercy. Only by the mercy of . . . bhaktyā mām abhijānāti. Bhaktyā mām abhijānāti (BG 18.55). Just like Kṛṣṇa is voluntarily offering Arjuna to understand Bhagavad-gītā. He's not going to canvass anyone. "Arjuna, you understand it. You'll be able to understand, because you are My devotee."