Years ago, when I lived in California, I was invited as a guest to a workshop seminar devoted to the design of long-term interstellar space missions. Various groups worked over the weekend on proposals for how such an enterprise should be structured and equipped, organized socially and politically, the designs for suitable craft, and so on. The attendees were a mix of technical people, economists, anthropologists, sociologists, and others. What struck me when they presented their conclusions in the afternoon of the final day was the zealousness that many displayed in seizing an opportunity to design a human society the way they thought it ought to be. But it seems to me that one of the surest recipes for trouble throughout human history has been the infliction on some people of other people's ideas of how they should live. Since nobody could know what circumstances or new experiences might arise on a voyage like that, wouldn't it be better to build in the flexibility to enable the people involved to satisfy their own preferences and create what was needed to adapt to whatever unforeseen problems actually transpired?
So instead of trying to decide ahead of time what kinds of physical structure and environment the inhabitants would have to live with, the departing mission could include a repository of construction material flying in formation with the ship--possibly supplemented by supply "rafts" sent on ahead--so that as dissident factions emerge and new generations of views appear, different groups can go out and build whatever they want. What better way, moreover, of curing restlessness and boredom, keeping essential skills alive from generation to generation, and putting surplus energies to constructive use? What arrives at the final destination would be a constellation of societies-in-miniature, many no doubt reflecting ideologies and social forms reminiscent of ones that existed on Earth, others, perhaps experiments in things totally different.
How, then, would those distant descendants eventually arrive at a habitable world orbiting some distant star? As a cooperative system of city states, eager to spread their culture across the surface? Or as mutually distrustful fortresses seeking only territory to enclose and defend? At the outset, of course, no one could know. But that's the whole point. The Migration tells the story of such a venture.