This is a wonderful essay, and I wish I had come across it as a freshman. For example: "Just as in the Maxwell theory, the abstract quality of the first-order

This is a wonderful essay, and I wish I had come across it as a freshman. For example: "Just as in the Maxwell theory, the abstract quality of the first-order quantities is revealed in the units in which they are expressed. For example, the Schrödinger wave-function is expressed in a unit which is the square root of an inverse cubic meter. This fact alone makes it clear that the wave-function is an abstraction, for ever hidden from our view. No-one will ever measure directly the square root of a cubic meter." That, of course, is an observation about quantum mechanics, and it is only on rereading the essay today that I noticed its structure: Dyson begins with an anecdote about Maxwell giving an address that spent most of its time discussing some features of Helmholz's "splendid hydro-dynamical theorems" (with a nod to Kelvin, who I guess was present), before briefly drawing analogies to his electrodynamical theory. Dyson brings this up within an essay in which he uses Maxwell's theory to make a point about coming to understand quantum mechanics, though he spends rather more time on his ultimate topic than Maxwell did in his talk.