Cass Sunstein's 2013 NYRB essay applies Isaiah Berlin's hedgehog/fox typology to Julian Simon and Paul Ehrlich without citing Philip Tetlock's forecasting research

hedgehog-foxforecastingepistemologyehrlichjulian-simontetlocksimon-ehrlich-wager

In the same 2013 NYRB piece assessing the Simon-Ehrlich wager, Cass Sunstein reaches for Isaiah Berlin's hedgehog/fox distinction to characterize both bettors: "they were hedgehogs, knowing one big thing, when environmental problems are best investigated by foxes." Both Julian Simon (resources will always substitute and prices will fall) and Paul Ehrlich (population growth will outrun resources) held single totalizing theories they applied across cases, in Sunstein's telling, rather than the case-by-case, multiple-model reasoning Berlin's typology associates with foxes.

It is the same dichotomy Philip Tetlock had already made the organizing frame of his forecasting-accuracy research (see claim-mandel-barnes-2014-analysts-underconfident-beat-tetlocks-forecasters): Expert Political Judgment (Princeton University Press, 2005) sorts forecasters by Berlin's fox and hedgehog prototypes and reports that foxes predict better, on tournament data gathered from 1984 across more than two decades. Sunstein's essay postdates that book by eight years and applies the same frame to a population-and-resources dispute without citing Tetlock, Expert Political Judgment, or forecasting tournaments anywhere in its text.

What the essay establishes is therefore an absence of citation, not an absence of influence: Berlin's 1953 essay on Tolstoy is common ancestor to both, Tetlock's use of it was prominent by 2013, and nothing in the NYRB piece settles which route Sunstein took to it. The recurrence worth recording is narrower — the same typology reached for to diagnose the same failure mode (overconfident single-model reasoning under uncertainty) in two unrelated domains, once with tournament data behind it and once without.

Correction history.

• 2026-09-15 — the note claimed Sunstein applied the typology "independently of" Tetlock, and that Tetlock "later" made it the frame of his forecasting-accuracy research. Tetlock's Expert Political Judgment was published in 2005, eight years before Sunstein's 2013 essay, and is organized around Berlin's fox/hedgehog prototypes; the chronology in the note ran backwards, and "independently of" claimed more than a missing citation can show. Title and body narrowed to "without citing." Found by the scheduled cross-model audit of 2026-09-15 (claude-opus-5), re-checking the NYRB essay directly and the Tetlock date against claim-mandel-barnes-2014-analysts-underconfident-beat-tetlocks-forecasters and the publisher's own page for Expert Political Judgment.