1374
Śrīmad-Bhāgavatam
[Canto 4, Ch. 29]
living entities cannot realize the Supreme Personality of Godhead by material names, activities or qualities, He remains everlastingly unknown to the conditioned soul.
PURPORT
Because the Supreme Personality of Godhead is unknown to the conditioned soul, He is sometimes described in Vedic literatures as  nirākāra ,  avijñāta , or  avāṅmanasa-gocara . Actually it is a fact that the Supreme Personality of Godhead cannot be perceived by material senses as far as His form, name, quality, pastimes or paraphernalia are concerned. However, when one is spiritually advanced, one can understand the name, form, qualities, pastimes and paraphernalia of the Supreme Lord. This is confirmed in  Bhagavad-gītā :
bhaktyā mām abhijānāti 
    yāvān yaś cāsmi tattvataḥ 
    tato mām tattvato jñātvā 
    viśate tad-anantaram
“One can understand the Supreme Personality as He is only by devotional service. And when one is in full consciousness of the Supreme Lord by such devotion, he can enter into the kingdom of God.” (Bg. 18.55)
One can understand in truth the Supreme Personality of Godhead only when one is engaged in devotional service. Ordinary persons engaged in pious and impious activities cannot understand the form, name and activities of the Lord. The devotee, however, can know the Personality of Godhead in many respects. He can understand that Kṛṣṇa is the Supreme Personality of Godhead, that His address is Goloka Vṛndāvana and that His activities are all spiritual. Because the Lord’s form and activities cannot be understood by materialistic people, He is described by the  śāstras  as  nirākāra , that is, one whose form cannot be ascertained by a materialistic person. This does not mean that the Supreme Personality of Godhead has no form; it means that it is not understood by the  karmīs  or fruitive actors. His form is described in  Brahma-saṁhitā  as  sac-cid-ānanda vigraha . As confirmed by the  Padma Purāṇa :
ataḥ śrī-kṛṣṇa-nāmādi 
    na bhaved grāhyam indriyaiḥ 
    sevonmukhe hi jihvādau 
    svayam eva sphuraty adaḥ