Māyāvādī philosophers think the universal form of the Lord to be real and His personal form illusory. We can understand their mistake by a simple example. A fire consists of three elements: heat and light, which are the energy of the fire, and the fire itself. Anyone can understand that the original fire is the reality and that the heat and light are simply the fire’s energy. Heat and light are the formless energies of fire, and in that sense they are unreal. Only the fire has form, and therefore it is the real form of the heat and light. As Kṛṣṇa states in Bhagavad-gītā (9.4) , mayā tatam idaṁ sarvaṁ jagad avyakta-mūrtinā: “By Me, in My unmanifested form. this entire universe is pervaded.” Thus the impersonal conception of the Lord is like the expansion of heat and light from a fire. In Bhagavad-gītā the Lord also says, mat-sthāni sarva-bhūtāni na cāhaṁ teṣv avasthitaḥ: the entire material creation is resting on Kṛṣṇa’s energy, either material, spiritual or marginal, but because His form is absent from the expansion of His energy, He is not personally present. This inconceivable expansion of the Supreme Lord’s energy is called acintya-śakti. Therefore no one can understand the real form of the Lord without becoming His devotee.