When was this doctrine first expounded, and what arguments, whether Biblical or otherwise, were given to support…[the doctrine of the one divine will]?
Proof of the Uniqueness of the Divine Will
1 Thess. 4:3 defines the divine will:
This is the will (θέλημα) of God: your sanctification (ἁγιασμὸς).
"ἁγιασμὸς" is related to the Greek word for "holy". There is only one Holy One, only one sanctification.
Also, Luke 22:42 shows the distinction between Christ's human will and the will of the Father (which is the divine will):
Father, if thou wilt, transfer this chalice from me. But yet not my will, but thine be done.
There is only one divine will because God is supremely simple.
God is His intelligence (intelligere), as St. Thomas Aquinas succinctly explains in his Compendium Theologiæ cap. 31:
God must be His own intelligence. Since “to understand” is second act, for example, to consider, whereas the corresponding first act is the intellect or knowledge, any intellect that is not its own understanding is related to its understanding as potency to act. For in the order of potencies and acts, what is first is always potential with respect to what follows, and what is last is perfective. This is true only with reference to one and the same being, for among different beings the converse obtains; thus a mover and an agent are related to the thing moved and actuated as act to potency. In God, however, who is pure act, there is nothing that is related to anything else as potency to act. Accordingly God must be His own intelligence.
Furthermore, the intellect is related to its act of understanding as essence is related to existence. But God understands through His essence, and His essence is His existence. Therefore His intellect is His act of understanding. And thus no composition is attributed to Him by the fact that He understands, since in Him intellect and understanding and intelligible species are not distinct; and these in turn are nothing else than His essence.
And God's will is identical to His intellect (Compendium Theologiæ cap. 33):
Evidently God’s will cannot be anything other than His intellect. For, since a good that is apprehended by the intellect is the object of the will, it moves the will and is the will’s act and perfection. In God, however, there is no distinction between mover and moved, act and potency, perfection and perfectible, as is clear from the truths we have already gained. Also, the divine intellect and the divine essence are identical. Therefore the will of God is not distinct from the divine intellect and God’s essence.
Another consideration: among the various perfections of things, the chief are intellect and will. A sign of this is that they are found in the nobler beings. But the perfections of all things are one in God, and this is His essence, as we showed above.” In God, therefore, intellect and will are identical with His essence.
Therefore, God is the divine will.
Since there is only one God, there can only be one divine will.
The asker down-voted and offered a constructive comment. Then a moderator deleted my answer, saying:
This doesn't answer the question that was asked at all. The question is one of history, not of proving a theological point.
the reason this post was deleted and the other one was not is that the other post addresses the historical issue of when and how the doctrine was introduced. Your answer does not, it only presents an apologetic for the doctrine which wasn't what the question was about. If you want further feedback or community review of this moderator action please ask about it on Christianity Meta.
How can one distinguish the difference between "present[ing] an apologetic for the doctrine" and "address[ing] the historical issue"? It seems all I have presented is the history of what theologians (St. Paul, St. Luke, and St. Thomas Aquinas) thought; I'm not doing original research.