If I want my world to have a global government that has real
authority, should I be thinking of it in terms of having taken a very
different path from Earth (e.g. a world conqueror), or is there some
sequence of events that could bring diverse sovereign states together
into a single world government?
Both, or rather either could end up working for you.
What conditions would have to be met in order for a world government
to take hold, and stick?
We will get to that.
Can you get to a world government through paths other than worldwide
Absolutely and frankly more likely.
Ok so we talk about Earth and government, but in reality what we are really talking about it people. Government is people, maybe the few (autocracy) maybe the many (democracy) or perhaps somewhere in-between.
People are what make world government such a hard concept to accept. We just seem to be wired to see difference as a threat, which may well be evolutionarily true, humans have been fighting each other and everything else for somewhere around 75,000 years and there is some evidence to suggest that humans fought with neanderthals and may have played a role in their extinction.
If we are functioning in an Earth setting, the only way I can see world governments uniting would be due to a very real, very dangerous and completely global threat. Alien invasion would be the obvious choice. Though I doubt this scenario would meet your make it stick criteria. Should we be destroyed, or win, things would likely devolve to some extent.
Even in this scenario though I doubt that there would be harmony across the planet, some will still fight for their various reasons.
Your mention of a world conqueror scenario is interesting but I find it implausible on the same merits as our real world earth. It's such a big space that controlling it via force is simply not practical.
On the other hand if we look at a totally different sentient species that evolved differently than humans it should be possible. Humans evolved in a darwinian system that favored aggressive behavior. If you can ensure that the species evolved in a less competitive environment (it would take longer, or perhaps be designed) the natural impulse to expand and breed and control could be less pronounced or possibly not there at all.
A designed species would likely be more plausible as the the effectiveness of evolutionary pressure is what drives advancement, and without it...do you ever get to a sentient species? Tough to say.
Point being, a less aggressive sentient species may not be in conflict and may more naturally be willing to compromise and work together.
Some other options that make a lot of sense:
- A hive mind but I don't think that is what you are looking for.
- A planet colonized by an alien species, in this scenario you start with a small population (on a planetary scale) and they work to build the planet up. Much easier to see how this would stay consolidated, particularly if they remain subservient to the power that established the colony in the first place.
On the nature of power. Power in a modern geopolitical sense is often broken down into a few parts.
- Information (Knowledge is power after all)
To truly dominate you would need to cover all of these aspects. You need a monopoly (or near monopoly) on the use of force. You need to oversee/control the levers of industry and finance. You need to be the top of the diplomatic pile, this is the soft skills portion where influence plays a huge role, can you diplomatically solve problems or get others in line? Finally information...this is touchy in the modern era obviously what with the potential impacts to personal freedom but information goes well beyond just personal data.
Nothing lasts forever but you could find ways to make a world government stick for varying lengths of time.