“To be realist about some concept is to say that there is such a thing, and it's not just made up by us, whereas to be nominalist, is to say it's just a way of speaking of ours, from the Latin 'nomen' word, just an empty sign. So for example, in the case of forces I was arguing for realism about forces. When you felt them by pressing the fingers together, you would naturally conclude from that that there is such a thing as forces. On the other hand you'd never be tempted to do that with something like the average Londoner. Scientists tell you that the average Londoner has 2.3 children; you're not tempted to think that that's anything except a way of speaking, that there's some individual entity called the average Londoner, that has 2.3 children. So it would be natural to take a realist view of forces, but a nominalist view of the average Londoner. There's this question about all the entities talked about in science. A classic case is numbers, so that's a very difficult one. Are there such things out there as numbers or are they just a way of speaking about the divisibility of things into parts or something?”I’m a nominalist about spectrum: I believe “spectrum” is just a way of speaking and does not have a referent in world. Most people, on the other hand, seem to be knee-jerk realists – “Of course there's such a thing as spectrum!” – though often when you start digging they become nominalists: “Of course, I don’t just mean frequency, there are lots of other factors…”
This fine philosophical distinction matters: If one takes the realist position, you behave as if there is a resource (spectrum) to be divided up and allocated, which leads ineluctably to radio licenses defined by hard frequency boundaries.
The nominalist perspective offers another way to thinking about the situation – for example, coordinating the operation of radio systems – that is just as valid. From a nominalist perspective the “coordination” view is just as (in)valid a perspective as “resource” view, and radio licenses don’t have to be defined primarily in terms of frequency and geography.
(See also my earlier post “Newton, Leibnitz and the (non?)existence of spectrum”. There the distinction was between the “absolutist” position that time and space are real objects in themselves, or the “relationalist” position that they are merely orderings upon actual objects that do not exist independently of the mind that is making the ordering.)