But they report (and there remains good marks of it to make it credible) that this was no island at first, but a part of the continent. Utopus, that conquered it (whose name it still carries, for Abraxa was its first name), brought the rude and uncivilised inhabitants into such a good government, and to that measure of politeness, that they now far excel all the rest of mankind. Having soon subdued them, he designed to separate them from the continent, and to bring the sea quite round them. To accomplish this he ordered a deep channel to be dug, fifteen miles long; and that the natives might not think he treated them like slaves, he not only forced the inhabitants, but also his own soldiers, to labor in carrying it on. As he set a vast number of men to work, he, beyond all men’s expectations, brought it to a speedy conclusion....
 They say the whole scheme of the town was designed at first by Utopus, but he left all that belonged to the ornament and improvement of it to be added by those that should come after him, that being too much for one man to bring to perfection. Their records, that contain the history of their town and State, are preserved with an exact care, and run backwards seventeen hundred and sixty years [244BC].
 At the first constitution of their government, Utopus having understood that before his coming among them the old inhabitants had been engaged in great quarrels concerning religion, by which they were so divided among themselves, that he found it an easy thing to conquer them, since, instead of uniting their forces against him, every different party in religion fought by themselves. After he had subdued them he made a law that every man might be of what religion he pleased, and might endeavor to draw others to it by the force of argument and by amicable and modest ways, but without bitterness against those of other opinions; but that he ought to use no other force but that of persuasion, and was neither to mix with it reproaches nor violence; and such as did otherwise were to be condemned to banishment or slavery. This law was made by Utopus, not only for preserving the public peace, which he saw suffered much by daily contentions and irreconcilable heats, but because he thought the interest of religion itself required it.--Thomas More, Utopia
While much of the narrative of book 2 of Utopia is focused on the present, the reader also learns quite a bit about the origin of the polity. While More himself is no Aristotelian, and so may be unmoved by this consideration, an explanation is incomplete without analysis of the origin, which is of independent interest.Above I have collected the three main passages pertaining to the pre-history and founding of Utopia.
We learn that its origin is in conquest. The original inhabitants lived on a peninsula. This peninsula was eminently defensible, but they lost their freedom for two reasons: first, they were technologically inferior to the conquerors; second, they were dis-unified due to religious disagreements. The latter is significant because it shows that the effects of religion on the dispositions conducive to unity cannot be ignored by those who wish to remain politically independent.
Unusually, the conquest is not followed by permanent subordination, slavery, or destruction of the original inhabitants by the conquerors. For the conquerors are force-ably leveled down and put to work. This has the symbolic significance that the conqueror and conquered are treated equally. It also symbolizes two further facts: first, it dignifies work and, in particular, public works. Second, no permanent leisure or extractive renter class is permitted to emerge. More subtly, Utopus is ehibited not just as a skillful military commander, but also a kind of despot capable of forcing his own followers to do things against their will (and presumably expectation).
In the previous paragraph I used 'public work.' But the digging of the channel turns the peninsula into an island. This exhibits the control by mankind over nature aimed at in Utopia (which anticipates New Atlantis in this respect).* A further effect is to turn the society into a fortified castle. While it's not the main focus of the description of Utopia, military prowess, even imperial conquest, is not an irrelevant element of its ongoing function (recall this post too).
As an aside, it's unclear how the initial succession of Utopus was arranged. But (eventually) Utopia has evolved into an elective principality. This prince is chosen for life but can be removed if he appears to wish to become a tyrant. He has power to punish crimes, and to pardon them (because he has kept the "prerogative.") In other respects the elected prince has not much further power (except that I assume he is at the head of armed forces).
To return to the main point. Utopus's design for utopia is deliberately unfinished in various respects; it presupposes the possibility of open-ended economic and aesthetic progress ('ornament and improvement'). I am not claiming that modernity is here first invented, but it is a notable break from the more cyclical template(s) that can be found in the classical models to which More richly alludes.
The possibility of open-ended progress can also be found (recall) in the laws of religion. This is an unusual mixture of requiring core doctrinal agreement about a few core dogmas -- in particular, that souls are immortal and will be punished/rewarded in the afterlife; that God is watchful and providential -- all of which quite clearly conducive to enforcing morality on earth, while simultaneously allowing religious innovation outside the core. However, such religious innovation is, in turn, constrained by the requirements of public order. (All of this anticipates the outlines of Spinoza's position.) The state religion is, with those qualifications, broadly ecumenical and tolerant in spirit. The underlying idea is the product of the fact that "Utopus judged it not fit to determine anything rashly; and seemed to doubt whether those different forms of religion might not all come from God, who might inspire man in a different manner, and be pleased with this variety." Underlying this is the providential idea -- often attributed to J.S. Mill -- that in the long run through the force of polite arguments truth will prevail "he imagined that the native force of truth would at last break forth and shine bright, if supported only by the strength of argument, and attended to with a gentle and unprejudiced mind.")
There is more to be said about this. But the important point is this. Utopus anticipates the Rousseau-ian legislator who introduces and sets a constitution on sound footing and then becomes dispensable. Notably, while there is room for technological and medical innovation on the island, there is little room for genuine political philosophy (or [recall] civilized philosophy) or even speculation (or school philosophy) on Utopia. Moreover, there is little evidence he was guided by such philosophy. This last point may be speculative, but it is made explicit in one of the poems (often attributed to Peter Gilles) that accompanied Utopia in its early printings.
with pleasure and solace.
I one of all other without philosophy,
Have shaped for many a philosophical city.
And mine I have nothing dangerous to impart,
So better to receive I am ready
with all my heart.*--probably Peter Gilles.
My only reservation is that the judgment on the philosophical character of Utopia (the city) is incomplete without further evaluation of the blue print in light of the conversations (and the different polities) described in Book I. But that's for another time.