Crackpot #physics theory of mine - On our trouble defining formally what an Observer is:

My hunch is that an observer is a selection of a partition of phase space (or maybe configuration space) in the set set of all valid partitions. For some notion of validity.

(Not) Coincidentally tied closely to how phi is computed in integrated information theory #IIT Which may provide a hint to how observers may relate to #consciousness via a functor between appropriate categories