observer

Any system that can take some stance toward the property in question (represent it, use it, treat-it-as, measure it).

E.g. a thermometer.

A pattern on the causal structure graph.
→ There can be no outside view on the structure, because the observer is part of it; and you cannot compute the next state without running it.

Are perspectives real? What is an observer?

Arguing about what something “really is doing” (as if there was only one true thing) is mistaken.
E.g. in biology, there are a variety of levels and sub-systems, observing each other and seeing different computations happening, each trying to squeeze out what it can.

Levin: “I come from a bit of an idealist perspective … What there are in the world is perspectives. When an observer sees something, that’s not just as if, but as real as it gets. If you can find, study, manipulate, … an observer that sees something. By seeing something and making use of it, you are making it real, and that’s what it means to be real.”

I agree 100%, but I don’t get what’s supposed to be idealist here.
It sounds like textbook materialism/Engels to me.

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