Going through my old posts on Less Wrong, I have found the first one that describes my version of instrumentalism:
The map/territory meme works better in some cases, worse in others. Note that it is only a model, not necessarily “the way things are”. A simpler and just as powerful approach is that repeatably testable models are all there is. It is tempting to assign repeatability of testing to the invisible unachievable “objective reality” behind the veil, something science strives to uncover, but this notion is unnecessary. If this makes you uncomfortable, do the standard exercise and reformulate the question such that it has an answer: “Why do I think that there is objective reality?”. (The answer turns out to be similar to that of “Why do I think I have free will?”)
Again, the minimal approach to the scientific method is: build models and test them. Adopt those with more experimentally confirmed predictive power. And by all means, use Bayes as an aid in constructing less-stupid models.
Typical reaction (just tested on #lesswrong, again):
But what are you testing your models *against*?
Me: who cares, you can pretend that they come from some thing called territory, which becomes one of your models
And on it goes, about the whether the spaceship disappearing behind the cosmological horizon ceases to exist and so on.