If you can spray them, they're real

Yessireeya. There it is once again: the age-old discussion between the realists and the instrumentalists.

It came up in a reply by Sander to my earlier posting on perception. Sander suggested that theories are only 'useful' and 'just mathematics'. Electrons are formulae, not real things. I replied quoting a philosopher who's name I'd forgotten, about spraying electrons, but it turned out that the example was about spraying photons (oh well) The correct story, with the name of the philosopher included, I refound on the web here.

'When Ian Hacking, for example, once asked a physics colleague what he was doing, the physicist replied that he was "spraying photons". Impressed, Hacking wrote: "From that day forth I've been a scientific realist. As far as I'm concerned, if you can spray them, then they are real."'

(I just love Google: I searched on "spraying" and "philosophy". Got a first hit!)

Turns out that this article that Google popped up for me is very interesting in itself. A researcher did an internet poll among physicists asking what kind of things they consider to be real, and which things they consider to be 'not real'. The list is long, including things like "concepts", "phlogiston", "electrons", "earth", "colours", basically everything you can name. He then writes a long review, discussing all issues involved, and along the way you basically learn about all the different philosophical positions one can possibly take.

Like, unreal dude!