In Zeph 2:11-14, we read the following oracle of divine judgment against Nineveh:
You also, O Ethiopians, shall be killed by my sword. And he will stretch out his hand against the north, and destroy Assyria; and he will make Nineveh a desolation, a dry waste like the desert. Herds shall lie down in it, every wild animal; the desert owl and the screech owl shall lodge on its capitals; the owl shall hoot at the window, the raven croak on the threshold; for its cedar work will be laid bare. (NRSV)
Then, in Zeph 2:15, the prophet writes:
It this the exultant city that lived secure, that said to itself, "I am, and there is no one else"? What a desolation it has become, a lair for wild animals! Everyone who passes by it hisses and shakes the fist. (NRSV)
Such a sentiment is paralleled by the Chaldeans who, personified in the Hebrew as a גְּבִירָה
(Great Lady/Queen/Queen Mother) compared herself thusly to other nations:
Sit in silence, and go into darkness, daughter of Chaldea! For you shall no more be called the mistress of kingdoms. I was angry with my people, I profaned my heritage; I gave them into your hand, you showed them no mercy; on the aged you made your yoke exceedingly heavy. You said, "I shall be mistress forever," so that you did not lay these things to heart or remember their end. Now therefore hear this, you lover of pleasures, who sit securely, who say in your heart, "I am, and there is no one besides me; I shall not sit as a widow or know the loss of children" (Isa 45:5-8 NRSV)
Such comments help us interpret texts such as Isa 43:10; 44:6, 8 where Yahweh says similar things. It would be impossible to argue that these cities believe that theirs were the only cities that had ontological existence and all other cities/nations did not have ontological existence; instead, such sentiments speak of their (self-professed) supremacy over all other cities/nations. Similarly, Yahweh in such texts is not speaking of the non-existence of other deities, but His supremacy over all other deities.
As I wrote elsewhere:
All nations before him are as nothing; and they are counted to him less than nothing, and vanity. (Isa 40:17)
The Hebrew locution, "as nothing" translates כְּאַיִן, which is rendered correctly by the KJV (an alternative translation would be like/as nought [cf. the NASB; 1985 JPS Tanakh]). The same locution appears in Isa 41:11:
Behold, all they that were incensed against thee shall be shamed and confounded: they shall be as nothing (כְאַיִן); and they that strive with thee shall perish.
Of course, this is a statement of the supremacy of Yahweh, not the denial of the ontological existence of nations apart from Israel.
In Isa 40:23, we read:
That bringeth the princes to nothing; he makes the judges of the earth as vanity.
Again, the term often translated as "nothing" or "nought" (Heb: אַיִן) is coupled with a pre-fixed preposition, in this instance, לְ ( לְאָיִן ). Again, the supremacy of Yahweh (and national Israel) is in view here, not the denial of the ontological existence of the princes in this verse who, obviously, have real existence, not imagined.
The term אַיִן often means "insufficient" or impotent, even in "Deutero-Isaiah" (Isa 40-47). Note the following:
And Lebanon is not sufficient (אַיִן) to burn, nor the beasts thereof sufficient (אַיִן) for a burnt offering. (Isa 40:16)
Again, the impotency of Yahweh's (and Israel's) enemies are in view here; not a denial of their ontological existence.