The word māyā is used in the sense of illusion. Considering the Supreme Personality of Godhead to be his own son, Mahārāja Nābhi was certainly in illusion, but this was transcendental illusion. This illusion is required; otherwise how can one accept the supreme father as his own son? The Supreme Lord appears as the son of one of His devotees, just as Lord Kṛṣṇa appeared as the son of Yaśodā and Nanda Mahārāja. These devotees could never think of their son as the Supreme Personality of Godhead, for such appreciation would hamper their relationship of parental love.