These arca forms of the Lord may be considered idols by the atheists, but that does not matter for persons like Vidura or His many other servants. The forms of the Lord are mentioned here as ananta-linga. Such forms of the Lord have unlimited potency, the same as that of the Lord Himself. There is no difference between the potencies of the arca and those of the personal forms of the Lord. The example of the postbox and post office may be applied here. The little postboxes distributed all over the city have the same potency as the postal system in general. The duty of the post office is to carry letters from one place to another. If one puts letters in postboxes authorized by the general post office, the function of carrying letters is performed without a doubt. Similarly, the arca-murti can also deliver the same unlimited potency of the Lord as when He is personally present. Vidura, therefore, could see nothing but Krsna in the different arca forms, and ultimately he was able to realize Krsna alone and nothing else.