If you actually can understand Kṛṣṇa through devotional service . . . not by challenging, not by mental speculation, not by meditation, not by fruitive activities. No. If you actually become a devotee and develop the consciousness of love for Kṛṣṇa, then God will be appreciated, God will be seen. Nāhaṁ prakāśaḥ sarvasya yoga-māyā (BG 7.25). Otherwise He'll not be visible. He's not exposed to the nondevotees. He's simply exposed, He can reveal Himself, sevonmukhe hi jihvādau svayam eva sphuraty adaḥ (Brs. 1.2.234), when one engages himself in the devotional service beginning with the tongue.
The devotional service begins with the tongue. Now, it is also another astonishment: service with the tongue. Yes. Service with the tongue means if you chant this Hare Kṛṣṇa mantra, that requires tongue. And if you simply take kṛṣṇa-prasāda, that requires tongue. With these two business of the tongue you can realize the Supreme Personality of Godhead. Chant Hare Kṛṣṇa and take kṛṣṇa-prasāda, and gradually you'll understand what is God. Therefore this word is used, sevonmukhe hi jihvādau svayam eva sphuraty adaḥ. Because by using the tongue you develop Kṛṣṇa consciousness, love for Kṛṣṇa consciousness.