Philosophers have spent quite a lot of time and words on discussing what is or isn't real (in one sense or another – and therein lies most of what there is to disagree about). As a physicist I care about what I get to observe, what patterns lie therein and what models I can build that can make sense of those patterns. Whether the observations at the root of that are an illusion, delusion, or other artefact of a system – perhaps an allegedly true reality behind my observations – that works completely differently than the models we come up with is of no interest to me at all. As long as the models physics comes up with suffice to account for the stuff I get to observe, I don't care.

I don't care whether I am a real thing – or an artefact of some delusions, of something in some truer description, that happen to cluster in a way that causes those delusions to have a sense of identity – or an emergent subclass of the sub-state processes of a finite state machine – or a subspace of a Hilbert space in which certain operators behave in certain ways – or, indeed, a neighbourhood of a smooth manifold – or any other model artefact that someone else feels like declaring to be the true reality; I only care that I get to observe certain signals that I find to fit certain patterns that are well modeled by certain formal systems – theories of physics. I don't care whether my delusion that I am observing something in my surroundings is any of the same kind of thing, just as long as what I do experience (delusional or fictive as even my existence, much less the sense of experiencing stuff that goes with it, may be) is tolerably well described by the models I'm using to make sense of them. In practice I define reality to be the stuff I experience, and tacitly presume that I really am something and my experience of experiencing stuff is a real thing – in particular, it's stuff that makes a big difference to what I experience; and making sense of it does enable me to respond to what I experience in ways that tend to lead to later experiences that I like better than the ones my model claims I would have experienced, had I behaved differently.

You are perfectly free to reject my delusions of the reality of me and my experiences. I do note, however, that I would not be writing this if I did not entertain the delusion that someone (possibly no-one but a later version of me) may at some point read it; I also invite you to notice that the very fact that you are reading this implicates you in humouring that delusion at least enough to allow that there is something you're reading. The very fact that we have a means of communication open to us, that lets me write this and you read it, says a great deal about the systematic structure of our experiences, which has made it useful to you to understand the written word and has tempted me – having seen the same usefulness for myself – into the delusion that there may be some point to writing something, that you're now reading, even if the whole of that point is to help me to remember this way of articulating the value of a naïve interpretation of the reality of my experiences.

Philosophical arguments about what is and isn't real are really about the semantics of that word real; when Newtonian fundamentalists denied the reality of the Coriolis and centrifugal forces – they're just artefacts of the spinning frame of reference – they were asserting that their model was the reality and the experiences of folk in spinning environments was illusory. Einstein subsequently showed how one can have a model (General Relativity) in which Coriolis and centrifucal forces are exactly as real as gravity – indeed, they are aspects of gravity, in the rotating frame. Either way, a kid sitting on a spinning roundabout and manipulating things in that environment would be able to observe the forces they describe. Philosophically, physicists side with the kid on the roundabout – no matter what your model may be, we care about what you actually observe. Philosophical positions that take some particular model as given and only consider things real if they are in some sense essential to the model, all else being illusion, are of no interest to physicists; and the only way for the philosophers who take such positions to settle the question of what is real is by declaring which model they have chosen to be sacrosanct, for whatever reasons. This is a social dynamic problem, that the philosophers are welcome to wallow in for as long as they like.

Meanwhile, physicists shall try to make sense of what we experience, while talking to each other and discovering that our delusion of having peers who experience essentially equivalent things is compatible with models we develop in conversation with those peers. When our social dynamics fails to settle a problem, we have a way of stepping outside the social dynamics and (metaphorically, at least) hitting something with a hammer to see how it responds, while describing to our peers the set-up and results we got, inviting them to repeat the experiment and tell us whether they get the same result. When we experience agreement with those peers, we trust that they'll accept our use of that shared experience as a grounds for consensus on what models are worth discussing. Whether you consider that consensus reality to be truly real, physicists have little reason to try to discuss any other reality with one another, aside from as an entertaining way to speculate about possible models we might build to describe the stuff our consensus says we get to experience.

Crucially, sane physicists distinguish between models that purport to describe reality and the stuff we experience – notwithstanding that our models may describe it all in ways far removed from a naïve account of our experience. To a physicist, what we experience is real: everything else is model.

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