Sustainability aims to stop making things worse. Regeneration aims to leave a system in better condition than you found it. The gap between those two ambitions is where the century is decided.
There is a reason the more modest goal is insufficient. If a system has already been drawn down — soils thinned, aquifers lowered, forests fragmented, populations reduced — then holding steady preserves the depletion. Sustaining a degraded state is not success. The only arithmetic that closes is one in which some things are put back.
Regenerative practice is not speculative. Agricultural methods that rebuild soil carbon and structure, forest restoration that follows ecological rather than plantation logic, fisheries managed for recovery, industrial design in which materials return to use rather than to landfill, and water systems designed for recharge rather than extraction — all of these exist, are practised at scale somewhere, and are documented. What limits them is rarely knowledge. It is time horizon, capital patience and the accounting conventions of Chapter Eight.
Notice the shape of what regeneration asks. It asks for work whose results arrive after the worker. A restored forest is legible in thirty years; rebuilt soil in ten to twenty; a recovered fishery in a decade at best. Every one of these is an act performed for a beneficiary the actor will not meet.