SB 3.27.17

Devahūti, the mother of Kapiladeva, the first inquiry is that in spite of understanding that a spirit soul and matter is different or the spirit soul is different from the matter, matter is different from spirit...

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...philosophical speculation or by proper understanding, actually the separation is not possible because the spirit soul is marginal potency of the Supreme Lord, and the matter is also external potency of the Lord. Somehow or other they have combined, but the potencies are eternal. Two eternal potencies are combined together, and so long they are combined together it is difficult to separate one from the another. So how it is possible that the individual soul can become liberated? Actually by practical experience one can see that when the soul is separated from the body, the body has practically no existence. And when the body is separated from the soul, one cannot perceive the existence of the soul. So, so long there is combination of the soul and the body, we can understand. But when they are differentiated or separated, practically there is no existence of the body and the soul. This question of Devahūti to Kapiladeva is more or less impelled by the understanding of the philosophy of voidism. Just like the voidists they say that this consciousness is the production of combination of matter; and as soon as the consciousness is gone, the material combination becomes dissolved and therefore ultimately there is nothing but voidness. Such absence of consciousness is called nirvana philosophy.