"The Supreme Personality of Godhead, Krsna, and His plenary portions cannot be understood by mental speculation nor by the nondevotees. If anyone wants to understand the Supreme Personality of Godhead, he has to take to pure devotional service under the guidance of a pure devotee. Otherwise, the truth of the Supreme Personality of Godhead will always be hidden. It is already stated (naham prakasah) that He is not revealed to everyone. Everyone cannot understand God simply by erudite scholarship or mental speculation. Only one who is actually engaged in Krsna consciousness and devotional service can understand what Krsna is."
(Bhagavad-gita, 18,56, Purport)
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