Environmentalists suggest we have a duty of care for the planet. If we had an invention which would reverse climate change but would make life impossible on earth in 200 years most people would suggest this would be to high a price to pay. But if the negative consequences were delayed 500 or 2000 years... do we have a duty to them? 700,000 years? Does orlimit of forward duty bear any rational scrutiny?

I don't see why not, we should bear in mind the consequences of what we do however far in the future those consequences stretch. What makes this difficult to think around though is that we are entitled to have some confidence that solutions will be found to problems that may arise in the future. This has been our experience in the past, disasters are constantly predicted when we extrapolate from the present to the future. Yet those very predictions so far have generally led to research that has obviated the putative dire consequences.

There is of course no guarantee that this will always be the case. It doers however make it difficult to take the thought experiment you set up very seriously.

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