The key to understanding mathiness is to recognize how a formal language can interact with natural language. The source code for a computer program has formal statements written in a language like C that will be interpreted by a compiler. It will also have comments and messages written in natural language that will be read by a person. Compared to mathematics, source code is easy to analyze because the statements in the two languages are kept separate.

After more than 100 years of incremental change, urban transportation is on the verge of a revolution. Last week, NYU’s Alain Bertaud brought together a small group with backgrounds that included transportation engineering, urban planning, economics, and applied physics, and who worked in the private sector, universities, think tanks, or government agencies in US, China, South Korea, and India to compare notes on what they are seeing. It soon became clear that our familiar words were getting in the way.

Dietz Vollrath has a new post that continues the discussion about how economists use math. He makes an important point (see #4 below) that I’ve tried to capture in the title and has also spurred a few other thoughts. DV: Romer’s motivation is irrelevant I agree with Dietz on this point. The attempts at starting a discussion about whether I am a bad person, and what sound like follow-on attempts at starting a discussion about whether Dietz is a bad person, need to be understood as evidence that the problems in the papers I criticize are real.

When I started this discussion about mathiness, I promised myself that I would publicly admit to any mistakes that I make. There is a post today at Information Transfer Economics that makes a good point: Romer should have left off the word empirical when he said: “Like mathematical theory, mathiness uses a mixture of words and symbols, but instead of making tight links, it leaves ample room for slippage between statements in natural versus formal language and between statements with theoretical as opposed to empirical content.

I have a rule about assigning blame: When a reader misunderstands, it is the writer’s fault. My paper and posts about mathiness have prompted some reactions that reflect a misunderstanding of my position. Here I’ll try to clarify what that position is. I’ll put off for later a response to people who understand (thank you!) but disagree. My position is hard to understand partly because it is unfamiliar. It is natural for a reader to think, “In criticizing mathiness, Romer has voiced a grievance that I/we have felt/articulated for years…” Or on the other side to think, “Romer has picked up that discredited argument that…”