“We may find some mailboxes on the street, and if we post our letters in those boxes, they will naturally go to their destination without difficulty. But any old box, or an imitation, which we may find somewhere, which is not authorized by the post office, will not do the work. Similarly, God has an authorized representation in the Deity form, which is called archa-vigraha. This archa-vigraha is an incarnation of the Supreme Lord. God will accept service through that form.” (Shrila Prabhupada, Bhagavad-gita, 12.5 Purport)