Bhāgavata says, ye 'nye 'ravindākṣa vimukta-māninaḥ: "If somebody thinks that he has become liberated after undergoing the process of impersonal philosophy and austerities and penances . . ." The impersonalists, they also practice severe penances to attain to that Brahman stage. That is also nice thing.
But they cannot stay there, because there is no enjoyment. Therefore, as I was saying the other day, that many sannyāsīs, they say that, "This world is false; Brahman is truth." So in spite of their rising to that platform of Brahman understanding, they again come down.
That is described in the Bhāgavatam, āruhya kṛcchreṇa paraṁ padaṁ tataḥ (SB 10.2.32) "After undergoing severe penances and austerities, they may rise to the Brahman platform but again falls down." Why falls down? Anādṛta-yuṣmad-aṅghrayaḥ: "Because they do not enjoy Your association." They have neglected the association of Kṛṣṇa and company. Therefore they have no, I mean to say, shelter.
The same example can be explained: just like if you go on a plane or sputnik very high, very high, that is void, all side void. If you go very high, 25,000 miles up, you'll see void. But that, there you cannot stay. You can travel for many years in that void, but if you don't take shelter in a planet, then you'll come back again to this planet. Similarly, the impersonalist, they cannot stay in their impersonal understanding. Simply they suffer some trouble. Kleśa . . . Bhagavad-gītā says, kleśo 'dhikataras teṣām avyaktāsakta-cetasām (BG 12.5). Those who are attached, those who are attached to that impersonal feature of the Absolute Truth, they undergo greater trouble.