Oh Jevons where art thou, really
? I had fun reading Tyler Cowen’s “The Marginal Revolution. Rise and Decline and the Pending AI Revolution”, a book about marginalism, “the economic doctrine that we can best understand value by considering the question of how many units of a good or service an individual has, and using that starting point to ask how much an additional – or marginal – unit would be worth in terms of other goods and services.” It’s a short and entertaining read, highly recommended. One thing I want to share is my discovery of William Stanley Jevons, the 19th Century British economist of paradoxical fame. The Jevons Paradox, while fun to tweet about and casually invoke, is probably the least important of his contributions. 1️⃣ Jevons carried the marginal revolution into the (dominant) Anglo-American research tradition. His core contribution was turning value from a substance (labor, as in Ricardo and Marx) into a rate, specifically, the rate at which utility changes at the margin. A concept now so baked into economics that students don't even notice it's a choice. His paradox belongs here: marginal cost decrease can lead to an increase in demand. 2️⃣ He wasn't just doing abstract theory. He treated utility as a real, measurable magnitude with social meaning, a mere representation of ordinal preference. His version kept the door open to interpersonal comparisons of welfare, which is exactly what you need if you want economics to say anything about redistribution, poverty, or social policy. 3️⃣ He was arguably the first (and last?) economist to insist that measurement beats dogma. His 1863 work on the fall in the value of gold was a serious technical contribution to index number theory, how to aggregate prices across goods to measure inflation or monetary depreciation. This is now the methodology behind every CPI calculation, every GDP deflator, every central bank inflation target. 4️⃣ Jevons moved political economy's foundation from "laws of mind" to "laws of physiology." That sounds obscure but it matters enormously. It's the ancestor of behavioral economics, neuroeconomics, and any approach that grounds economic behavior in biological or psychological mechanisms rather than pure rational deliberation. Jevons was gesturing toward what we'd now call the science of decision-making, before the tools existed to pursue it properly. 💡 The through-line is that Jevons was essentially building the scaffolding for three different futures simultaneously: formal neoclassical theory, empirical measurement economics, and socially-grounded welfare analysis. The profession mostly ran with the first, partially with the second, and kept arguing about the third. That's a pretty remarkable range of influence for someone who drowned at 46 and whose obituary led with his contributions to logic.