Prabhupāda: Just like we have no knowledge of Kṛṣṇa, conditioned soul. Therefore for our understanding, He is so merciful, He descends as arcā-mūrti. This Deity which we are worshiping, that is called arcāvatāra, incarnation of arcā. He's accepting our worship, our prayer, our everything. He has descended just suitable for our handling. That is His mercy. Therefore we should not consider that this arcā Kṛṣṇa is made of stone, as atheists will say that, "These foolish persons are worshiping. Heathens, they are worshiping." No, we are not worshiping stone. We are worshiping Kṛṣṇa. But that they do not know. Kṛṣṇa has appeared before us. Because at the present moment, we cannot see except stone and wood, therefore, suitable for our vision, He has appeared in such a way. Otherwise, how we can appreciate?
Here . . . they are searching after what is God, but here is God. Here is God. Therefore in the śāstra it is forbidden, arcā . . . arcye viṣṇau śilā-dhīr guruṣu nara-matir vaiṣṇave jāti-buddhiḥ (Padma Purāṇa). It is forbidden, that when you worship Deity, you should not think that it is made of wood or stone or something else material. No. What is this material? Material is . . . matter means the energy of Kṛṣṇa. Just like the sunshine, or like the illumination of this light: it is the energy of the lamp. So it is not different. Similarly, as Kṛṣṇa says in the Bhagavad-gītā, bhūmir āpo 'nalo vāyuḥ (BG 7.4), this earth, water, air, fire, anything material, that is expansion of His energy.
So He can accept your service through His energy. That is His omnipotency. That is called omnipotency. You cannot do anything of your personal affairs with your energy, but . . . you can sometimes do. Suppose if you have got money. Even being present on the spot, by spending money you can get the things done. The money will act for you. Similarly, Kṛṣṇa being omnipotent, He can take your service through His agency, through His potency. And potency means śakti. Śakti-śaktimator abhedaḥ. Kṛṣṇa and His potency is not different. So Kṛṣṇa, by His causeless mercy, He has appeared before you in a manner by which you can touch Him, you can handle Him, you can dress Him, you can give Him. This is Kṛṣṇa's mercy. It is not idol worship. Therefore it is forbidden. Don't think it is idol.
(aside) Go on.
Pradyumna: "Thus the Bhagavad-gītā or any authentic scriptural sound representation of the Lord is also the incarnation of the Lord. There is no difference between the sound representation of the Lord and the Lord Himself. One can derive the same benefit from the Bhagavad-gītā as Arjuna did in the personal presence of the Lord."
Prabhupāda: You can derive the same benefit as Arjuna by reading Bhagavad-gītā. People say that Arjuna was enlightened because Kṛṣṇa was present before Him. But Kṛṣṇa is present before you also—by His words, by His sound representation. Just like Hare Kṛṣṇa mantra, Kṛṣṇa's name, it is not different from Kṛṣṇa. Nāma . . . abhinnatvān nāma-nāminoḥ (CC Madhya 17.133). Nāmi . . . here in the material world the name and the person whose name, that is different because it is material. If you want water, this water this substance, or water is different from the name water.
You cannot quench your thirst simply by chanting "water, water." That is not possible, because it is material. But you can realize the Supreme Personality of Godhead by chanting Hare Kṛṣṇa mantra. That is the significance of spiritual and material. Otherwise, how people are satisfied simply by chanting Hare Kṛṣṇa mantra? Let him chant some other name, material. No. You cannot chant more than three times. Then you will feel tired. But you can go on chanting Hare Kṛṣṇa mahā-mantra for hundreds and millions of years; it will . . . still you will not feel tired. That is the difference. Therefore His name and He is not different. Abhinnatva.