"Artists need to be in there from the start, making the argument for quality. The key to this thing is, for example, if you give an engineer a set of criteria which does not include a quality quotient, as it were—that is, if this sense of the quality, the character of the place, is not a part of his original motivation—he will then basically put the road straight down the middle. He has no reason to curve it. But if I can convince him that quality is absolutely a worthwhile thing and we can work out a way in which the road can be efficient and also wander down by the river, then we essentially have both: he provides his sort of expertise in that the road works, I provide quality in that it passes by the river. In that way, art gets built into the criteria from the beginning rather than being added on afterward."

But over the past decade, Boston has fallen ill with a grave case of the Architecture of Right Now. Featureless glass — or even worse, plastic-cladded — high-rises in a minimalist or deconstructive style have been steadily replacing or crowding out beloved older buildings. As the new structures, which overwhelmingly lack traditional architectural elements or ornamentation, ooze across more of what used to be a defiantly unique cityscape, the overall effect is like that of being conquered by especially tasteless barbarians.

For the first time in history, many high-status buildings have little or no ornament. Although a trained eye will recognize more ornamental features in modern architecture than laypeople do, as a broad generalization it is obviously true that we ornament major buildings far less than most architectural cultures did historically. This has been celebrated by some and lamented by others. But it is inarguable that it has greatly changed the face of all modern settlements. To the extent that we care about how our towns and cities look, it is of enormous importance.

The naive explanation for the decline of ornament is that the people commissioning and designing buildings stopped wanting it, influenced by modernist ideas in art and design. In the language of economists, this is a demand-side explanation: it has to do with how buyers and designers want buildings to be. The demand-side explanation comes in many variants and with many different emotional overlays. But some version of it is what most people, both pro-ornament and anti-ornament, naturally assume.

However, there is also a sophisticated explanation. The sophisticated explanation says that ornament declined because of the rising cost of labor. Ornament, it is said, is labor-intensive: it is made up of small, fiddly things that require far more bespoke attention than other architectural elements do. Until the nineteenth century, this was not a problem, because labor was cheap. But in the twentieth century, technology transformed this situation. Technology did not make us worse at, say, hand-carving stone ornament, but it made us much better at other things, including virtually all kinds of manufacturing and many kinds of services. So the opportunity cost of hand-carving ornament rose. This effect was famously described by the economist William J Baumol in the 1960s, and in economics it is known as Baumol’s cost disease.