The post office gives you a letterbox in front of your house. But that little box is not a letter . . . an ordinary box; it is post office. It is post office actually. If you imitate a box like that, and if you put your letter, that will not go. But in that authorized box if you put your letters, it will go any part of the world. So that box, do not consider that it is ordinary box. It is the whole post office, whole postal department. But for your convenience the postal department has come before you like a small box.
Similarly Kṛṣṇa, arcā-mūrti . . . everyone knows that this mūrti is made of stone or wood or metal. But it is not that. Kṛṣṇa is all-powerful. He can take your service in any way. But the point is that because you cannot see beyond this metal and wood and stone, therefore He comes in that form, so that you can see. This is the point.
Don't be carried away by the nonsense philosophy that "These people are worshiping idol." It is not idol. It is same example: He is Kṛṣṇa Himself. Always same. He is Kṛṣṇa Himself. He has come to you for . . . just you can see Him. That's all. Otherwise Kṛṣṇa, ataḥśrī-kṛṣṇa-nāmādi na bhaved grāhyam indriyaiḥ (CC Madhya 17.136)—with these blunt eyes, material eyes, you cannot see Kṛṣṇa at the present moment.