The sentence was Keynes's response to the Treasury view that inflationary pressures would resolve themselves as the economy returned to equilibrium. Keynes's point was not that the long run is unreal but that it is a misleading guide to current policy — that the interval between disruption and adjustment is where the economic problem actually lives.
The AI application is direct. The optimist's argument that every previous technological transition eventually produced net expansion is empirically correct. The mechanization of agriculture displaced ninety percent of farm workers; their descendants work in industries that could not have been anticipated. The pattern is real — and operates on timescales of decades.
The AI displacement operates on timescales of months. The gap between the speed of displacement and the speed of institutional absorption is not a coordination problem. It is a structural failure that determines whether the transition produces broadly distributed expansion or concentrated gain with widespread suffering.
The Luddites exemplify the point. They were right about the short run — their wages collapsed, their communities dissolved. Their grandchildren, eventually, participated in the industrial expansion. The Luddites, who lived in the short run, did not benefit. The honest response to the optimist's long-run argument is not to deny its correctness but to insist on the institutional response that bridges the path.
The sentence appears in Keynes's A Tract on Monetary Reform (1923), in the chapter on the theory of money.
Methodological, not flippant. The sentence articulates a commitment to policy relevance over theoretical purity.
The path matters. Economic analysis must address the trajectory, not merely the endpoint.
Short-run moral priority. The generation living through a transition cannot eat the promise of long-run equilibrium.
AI compression. When transitions compress from decades to months, the gap between disruption and adjustment becomes the entire problem.
Institutional bridge. The role of institutions is to sustain human beings during the path — the interval the long-run argument dismisses.