Supreme knowledge comes from hearing about Krishna directly from God Himself, not from endless mental speculation.Listen — Srila Prabhupada Uvaca
Bhagavad-gītā 7.1 — December 13, 1972, Ahmedabad 721213BG-AHMEDABAD [54:42 Minutes] Bg-07.01_721213BG-AHMEDABAD Prabhupāda: mayy āsakta-manāḥ pārtha yogaṁ yuñjan mad-āśrayaḥ asaṁśayam samagraṁ māṁ yathā jñāsyasi tac chṛṇu [Bg. 7.1] So by the end of the Sixth Chapter, Kṛṣṇa has explained the aṣṭa, aṣṭāṅga-yoga-siddhi. Aṣṭāṅga-yoga-siddhi, that yoginām api sarveṣāṁ mad-gatenāntar-ātmanā [Bg. 6.47]: always who is thinking of Kṛṣṇa within himself, śraddhāvān, with faith and knowledge, he is first-class yogī. So how this first-class yoga system helps me? Because the other yoga system, they will disagree, that "Simply by thinking of Kṛṣṇa within one's heart, how one becomes perfect?" That is explained from the Seventh Chapter of Bhagavad-gītā, how simply by understanding Kṛṣṇa you become well aware of everything, this yoga system.
In the Vedas also it is stated, yasmin vijñāte sarvam idaṁ vijñātaṁ bhavati [Muṇḍaka Upaniṣad 1.3]. If you, if you simply understand Kṛṣṇa, then you know everything. Kṛṣṇa is the root of everything. Therefore Kṛṣṇa says, śrī-bhagavān uvāca.
We should always remember that this Bhagavad-gītā is being spoken by the Supreme Personality of Godhead. So no more better authority. And God is speaking about Himself. Otherwise, by speculation you cannot understand God.
That is not possible. You have to hear from God Himself about God. athāpi te deva padāmbuja-dvayaprasāda-leśānugṛhīta eva hi jānāti tattvaṁ bhagavan... na cānya eko 'pi ciraṁ vicinvan [SB 10.14.29] "A person who has got little favor," athāpi te deva padāmbu..., "little favor from the lotus feet of Your Lordship, he," jānāti tattvam, "he knows what is tattva, what is the Absolute Truth." Athāpi te deva padāmbuja-dvaya-prasāda-leśānu..., prasāda-leśa: little favor, not all. Prasāda-leśānugṛhīta eva hi jānāti tattvam, na ca anya ciraṁ vicinvan. Others may go on speculating for years and years, it is not possible to understand. So similarly, in the Brahmā-saṁhitā, another Vedic literature, it is said, panthās tu koṭi-śata-vatsara-sampragamyo vāyor athāpi manaso muni-puṅgavānām [Bs. 5.34].
Muni-puṅgavānām, great saintly persons, sages, if they travel for millions of years... Panthās tu koṭi-śata-vatsara. Koṭi, again multiplied by hundreds and hundreds. Vāyor athāpi: on the airplane of air. Not this metal airplane, but actually air airplane or by the airplane of mind.
Mind speed we know. Mind can run within a second many thousands of miles, immediately. Suppose I am sitting here. So I have got my apartment in Los Angeles, ten thousand miles away.
I can immediately go... This is called mind-speed. So with the mind speed, with the velocity of air, if one runs on, to find out the Kṛṣṇa planet, or Kṛṣṇa, still, avicintya-tattva, still, it is inconceivable tattva. panthās tu koṭi-śata-vatsara-sampragamyo vāyor athāpi manaso muni-puṅgavānām so 'py asti yat-prapada-sīmny avicintya-tattve govindam ādi-puruṣaṁ tam ahaṁ bhajāmi [Bs. 5.34] Govinda is very, very difficult to understand by mental speculation, philosophical theses. Philosophical theses, speculation, without religion is simply waste of time. And religion without philosophical basis is sentiment.