This is confirmed in the Brahma-saṁhitā (5.38):
- premāñjana-cchurita-bhakti-vilocanena
- santaḥ sadaiva hṛdayeṣu vilokayanti
- yaṁ śyāmasundaram acintya-guṇa-svarūpaṁ
- govindam ādi-puruṣaṁ tam ahaṁ bhajāmi
I worship Govinda, the primeval Lord, who is Śyāmasundara, Kṛṣṇa Himself with innumerable inconceivable attributes, whom the pure devotees see in their heart of hearts with the eye of devotion tinged with the salve of love.
Therefore, the scriptural conclusion is that mundane philosophers like Dr. Radhakrishnan are not qualified to delve into spiritual subjects. The devotees of the Lord alone are eligible to understand Lord Kṛṣṇa; no one else is qualified. As Kṛṣṇa Himself states in the Bhagavad-gītā, bhaktyā mām abhijānāti yāvān yaś cāsmi tattvataḥ: (BG 18.55) "One can understand Me as I am, as the Supreme Personality of Godhead, only by devotional service."