In his 1850 essay "That Which Is Seen, and That Which Is Not Seen," the French economist Frédéric Bastiat told the parable of a shopkeeper whose son breaks a window. A bystander consoles the shopkeeper by arguing that the glazier will now have work, which benefits the economy. Bastiat's rejoinder — that the shopkeeper would have spent the same money on something else, and that society is now poorer by one window — is the canonical statement of the opportunity-cost critique of destruction-as-stimulus. The parable has remained relevant because the argument it refutes has remained popular.
The recurring claim
Across the twentieth and twenty-first centuries, commentators have periodically argued that major wars "ended the Great Depression," that reconstruction "boosts GDP," or that defense spending is a superior form of stimulus. The measurements cited — increased industrial output, reduced unemployment, accelerated technological development — are real. What they leave out is the counterfactual: the civilian capital, human lives, and accumulated infrastructure that the same inputs could have produced instead. GDP is a flow measure that does not debit destruction.
What the data actually shows
Careful economic histories of wartime mobilization generally find that aggregate productive capacity does rise during mobilization, but that per-capita welfare falls, consumption is rationed, and postwar recovery consumes years of accumulated savings. The "stimulus" effect is better read as an emergency exit from coordination failure — if a society is stuck below its production frontier, any sufficiently large shock can restart it — not as evidence that destruction itself creates wealth. Post-War Reconstruction treats the recovery side explicitly.
The abundance-era opportunity cost
Bastiat's argument becomes sharper as productive capacity grows. In a subsistence economy, the glazier's work at least ensures someone is fed; in an abundance economy, the foregone alternatives — the clinic not built, the model not trained, the habitat not restored — represent welfare gains orders of magnitude above what the repair recaptures. The more capable a civilization becomes, the larger the gap between the seen (repair) and the unseen (the abundance it displaced). See Post-Scarcity Economics.
Open questions
Are there cases in which destruction is net-productive through the forced replacement of obsolete capital — a "creative destruction" reading? Some economists argue that wartime urgency accelerated technologies (radar, jet engines, antibiotics, nuclear power, the early internet) that peacetime markets would have reached more slowly. The honest response is that acceleration under duress is not free — it comes at enormous human cost — and that deliberate abundance-era investment could in principle achieve the same acceleration without the destruction.