The secret of success in understanding the intricacies of knowledge of the Absolute Truth, the Personality of Godhead, is the causeless mercy of the Lord. Even in the material world, the father of many sons discloses the secret of his position to the pet sons. The father discloses the confidence unto the son whom he thinks worthy. An important man in the social order can be known by his mercy only. Similarly, one must be very dear to the Lord in order to know the Lord. The Lord is unlimited; no one can know Him completely, but one's advancement in the transcendental loving service of the Lord can make one eligible to know the Lord. Here we can see that the Lord is sufficiently pleased with Brahmājī, and therefore He offers His causeless mercy to him so that Brahmājī may have the factual realization of the Lord by His mercy only.
In the Vedas also it is said that a person cannot know the Absolute Truth Personality of Godhead simply by dint of mundane education or intellectual gymnastics. One can know the Supreme Truth if one has unflinching faith in the bona fide spiritual master as well as in the Lord. Such a faithful person, even though illiterate in the mundane sense, can know the Lord automatically by the mercy of the Lord. In the Bhagavad-gītā also, it is said that the Lord reserves the right of not being exposed to everyone, and He keeps Himself concealed from the faithless by His yoga-māyā potency.
To the faithful the Lord reveals Himself in His form, quality and pastimes. The Lord is not formless, as wrongly conceived by the impersonalist, but His form is not like one that we have experienced. The Lord discloses His form, even to the extent of measurement, to His pure devotees, and that is the meaning of yāvān, as explained by Śrīla Jīva Gosvāmī, the greatest scholar of Śrīmad-Bhāgavatam.