Through mental speculation, even the greatest philosopher cannot know the Supreme Lord, who is the Absolute Personality of Godhead. He can be known only by His devotees through His mercy. In the Brahma-saṁhitā (5.34) it is stated that even if a nondevotee philosopher travels through space at the speed of the wind or the mind for hundreds of millions of years, he will still find that the Absolute Truth is far, far away from him.