Our world is a world where a rainbow could be.
At first, there was a world that only received and returned no dividends. Its inhabitants took no ownership. They lived with their Creator's benevolence, they did what they did with no need for excuses, and eventually died as they died. And that was it.
With the Flood, this world was recreated. The earth was cleansed, the atmosphere purified. It became a world that could take the sunshine that poured in from above and refract it into many colors.
It became a world where a created being could be born, take the soul, body, share of the world and all the sustenance its Maker gave to it, use that, do something with that—and then return it, saying, "See what I have done with that which You gave me!"
And so, G‑d vowed to never destroy the world again. For, if the inhabitants would go wrong, they might always turn around and clean up their own mess.