Tyler Cowen is an economist, educator, intellectual, and fellow member of the commentariat (though plenty more eloquent and prolific than me). He's out with a new book... which he describes as "Not quite a book"

It has four chapters, is about 40,000 words, is fully written by me (not a word from the AIs), and it is attached to an AI with a dual page display, in this case Claude.  Think of it as a non-fiction novella of sorts, you can access it here.  You can read it on the screen, turn it into a pdf (and upload into your own AI), send it to your Kindle, or discuss it with Claude.

This is a 4-part series — corresponding to the four parts of Cowen's "book" — where I share some extracts and comments from the book as I'm making my way through it. You can read Chapter 1 here.

The full book, The Marginal Revolution: Rise and Decline, and the Pending AI Revolution, is available here:
https://tylercowen.com/wp-content/uploads/2026/03/TheMarginalRevolution-Tyler_Cowen.pdf

(giving it away openly, like Max Hillebrand did for Praxeology of Privacy is very cypherpunky... and also fits exactly with the times, where the value of generated written art or content drops to zero... so creators might as well give it away. I'm on this theme all the time, #796401, #1467035)

CHAPTER 2: William Stanley Jevons, Builder and Destroyer of MarginalismCHAPTER 2: William Stanley Jevons, Builder and Destroyer of Marginalism

It's not super obvious to me why Cowen focuses so much on Jevons — but then again, I'm trained in the Austrian branch of marginalism, the descendants that follow Menger instead of Jevons. In part, for something Cowen brings up later (p. 43): "Contrary to the other marginalists, Jevons seemed to think that utility had intrinsic, cardinal “social meaning".” (plus the mathematicizing of things, the excessive emphasis on measurements... average-ism, Cowen calls it.)

or here (p. 51):

He doesn't elaborate too much (or I missed it?) on why Jevons' flavor carried the seeds of its own destruction... I can triangulate and thing "compute," "math" but I'm not sure that's the interpretation Cowen brings.

Cowen describes Jevons as arrogant and precocious… neither of which I know is accurate (don’t know the converse either). For ~BooksAndArticles fans, we learn that Jevons was a total bookworm:

Jevons also was a “born collector” in the words of Keynes, and an extreme bibliomaniac. He accumulated thousands of books, and he lined the walls of his house and attic with them, and also stored them in piles in the attic, which became a problem for his wife upon his passing. (p. 36)

Marginal Utility

The canonical form of Jevons’s theory of marginal utility was outlined in his 1871 The Theory of Political Economy. Throughout the book, Jevons knew he was on to something special, and he knew he finally had worked the idea out, albeit not fully. [...] he knew he would be dragging British classical economics away from its obsession with cost and costs of production.
He stressed that the entire mainstream Ricardian apparatus would have to be abandoned, and that the classical economists were wrong about distribution, and their fears that rent would absorb an increasing amount of the social surplus (p. 38, p. 40)

"His key framing is that the allocation of any commodity or money will be performed in a manner to equalize its marginal return in any use." (p. 39)"His key framing is that the allocation of any commodity or money will be performed in a manner to equalize its marginal return in any use." (p. 39)

The title of the book, and already earlier in the chapter, we've gotten hints about AI and Jevons Paradox (where a higher efficiency of a fuel leads to more, not less, usage)

Jevons’s real contribution comes in chapter seven “Of the economy of fuel,” where he presents a decidedly marginalist argument, though without recognizing it as such in 1865. Jevons is pessimistic about the ability of conservation to extend the supply of coal indefinitely. Let us say for instance that energy use becomes more efficient. In the short run, the effect is more conservation. But to use modern terminology, the price of energy, coal-based or otherwise, has declined. With energy prices lower at the margin, we will in turn use more energy. Much of the initial savings from conservation will be exhausted by the new, greater demand for energy. This is now called “The Jevons Paradox,” and it is a central idea in environmental economics, especially when conservation is discussed (p. 41)

This is a modern-af convo (and probs why Cowen, ever the intellectual trend-follower, started onto this investigation in the first place):

Would the Jevons Paradox hold, or more concretely, would the demand for high-quality chips go up or down? On one hand, a kind of conservation was achieved, namely, that a great system could be built with fewer chips. That should, at least in the short run, lower chip demand. On the other hand, this will over time increase the demand for AI services and also the demand for chips. How are the net effects going to fall?” (p. 42)

p. 45:

Marginalism and averagism together… metrics, Can we say that for Jevons it was the marginal that ruled in theory, but the average that ruled in measurement and practice? And this is not just a statement about Jevons. His entire historical period saw both the rise of marginalism but also the rise of quantitative and statistical techniques in economics and the other social sciences. “Marginalism” and “averageism” came together, as part and parcel of the same package.

Jevons saw the important difference

In The Theory of Political Economy he emphasizes the difference between the individual and the average. He notes that marginalist theory presumes to investigate the individual mind, but much of the actual action in economics comes at the level of aggregates. What we now call the law of demand, for Jevons, operates at the aggregate level, not the individual level. (p. 46)

The price of everything, yet the value of nothingThe price of everything, yet the value of nothing

That economists supposedly know the price of everything and the value of nothing, is right theeere in the discipline's founding.

If you look at the introduction to The Theory of Political Economy, the first page is spent outlining the marginalist idea. Immediately thereafter, Jevons spends pages arguing for quantification and the unity of the social and mechanistic sciences. For Jevons, The Theory of Political Economy really was a plea for two distinct revolutions, not just what we now call the marginal revolution but a quantitative and statistical revolution as well. (p. 47)

“this emphasis on the empirical helps explain why Jevons and not his precursors drove the marginal revolution” (p. 52)“this emphasis on the empirical helps explain why Jevons and not his precursors drove the marginal revolution” (p. 52)

In sum, Jevons was the engineer’s economist. He turned value into a rate, built a machine to test inference, and insisted that measurement beats dogma. He got some calls wrong (sunspots), but he made the marginal intellectually irresistible. In the AI era, when efficiency gains seem to promise frugality and deliver expansion, the Jevons Paradox returns as a live policy question. At the margin that is of course. (p. 56)