I don't feel that you have tried to answer my questions, but let's keep pretending this is a conversation and I will react to your points.

> This means that the imminent concern in the capacity of sustainability (exacerbation of climate change) is largely addressed, save for the carbon capture / cooling aspect we will want.

This seems to show that you have a climate-only lens to look at the problem, even though the point that fusion would greatly disrupt CO2 emissions is 100% correct. The imminent concern is not just exacerbation of climate change.

1) This lens is incomplete because even if we completely stopped emitting CO2 right now we would still go to a destabilisation of the physical world around us due to all the other planetary boundaries being crossed https://www.stockholmresilience.org/research/planetary-bound.... For example food supply would be disrupted by the artificialization of soils and disruption of the Phosphorus Cycle, many if not most food chains on which we depend will collapse due to the fact that we are killing or consuming most animal species, among which vital insects (the 6th mass extinction has started and is much faster than previous mass extinctions), water supply will be disrupted more and more etc.

2) It's also incomplete because it doesn't account for the other end of the problem : the depletion of ressources. Fusion means we can extract more and more resources, deeper and deeper, creating an even more unbalanced system if it's not done in a way were resources can regenerate themselves at the same rate we extract them.

With what we have done every time we got additional energy so far, it is likely that getting fusion will increase pressure on planetary boundaries that are not CO2 emissions : you fix a problem by worsening the others.

> it makes no sense to assume the same level of depletion. It's a function of demand.

Good point. It's a function of demand, therefore it makes sense to assume the same level of depletion will increase, since more and more people will get access to middle-class (or more) lifestyle, which is the main driver of demand for resources (as opposed to population growth, which is less of a driver if it's population growth in countries without a middle class).

> This also doesn't take into account technological innovation.

As I said this could be a factor that helps with depleting less resources but so far we have observed the impact technology has been to dramatically increase ressource use and waste overall, not reduce them.

> The rich are too few in number and they're primarily rich by virtue of everyone else's consumption. Notwithstanding that their own practices can be very damaging, it doesn't meet that scale.

We are talking about middle classes here, which are massive and meant to become even more massive. It is also true that the richer you are the more you emit but that's a side phenomenon to understand why the amount of middle-class matters.

> There's no evidence that a zero-carbon world with improved energy efficiency would necessarily lead to environmental destruction.

Then you haven't read or studied resources like https://www.stockholmresilience.org/research/planetary-bound... to begin with a simple/mainstream one for example, you haven't looked at the impact of mining and the orders of magnitude of resources we would need for a world where societies keep having the same behaviour as today, with just the "carbon-free" component added.

Anyway this is a bet: there is no proof it would work either, and if it does not the population will completely collapse. Which way do you want to try? An organised de-growth (in terms of GDP, not total wealth if we account for the destruction of nature) were we know we can make it at the expense of less comfort and consumerism, or try to keep growing and just become net zero carbon, with the hope that we can make it, to the risk of collapsing and making the earth uninhabitable?

One more resource you can look at in case you didn't know about it: https://en.wikipedia.org/wiki/The_Limits_to_Growth#:~:text=T...

Being obsessed with carbon creates blindspots with respect to all the other planetary limits, our oceans are being emptied of life because of what we have done so far with abundant energy. The earth system is being destabilised in many other ways than just climate change. We need a global systemic solution, not to fix the problems one by one separately, because by doing that you will often make other problems worse by fixing one.

I'm not saying we don't need more abundant energy, I'm saying we need to change our philosophy, the way we organise ourselves and what we do with it first.