  In physics, there is the prevailing intuition that we are part of a unique
external world, and that the goal of physics is to understand and describe this
world. This assumption of the fundamentality of objective reality is often seen
as a major prerequisite of any kind of scientific reasoning. However, here I
argue that we should consider relaxing this assumption in a specific way in
some contexts. Namely, there is a collection of open questions in and around
physics that can arguably be addressed in a substantially more consistent and
rigorous way if we consider the possibility that the first-person perspective
is ultimately more fundamental than our usual notion of external world. These
are questions like: which probabilities should an observer assign to future
experiences if she is told that she will be simulated on a computer? How should
we think of cosmology's Boltzmann brain problem, and what can we learn from the
fact that measurements in quantum theory seem to do more than just reveal
preexisting properties? Why are there simple computable laws of physics in the
first place? This note summarizes a longer companion paper which constructs a
mathematically rigorous theory along those lines, suggesting a simple and
unified framework (rooted in algorithmic information theory) to address
questions like those above. It is not meant as a "theory of everything" (in
fact, it predicts its own limitations), but it shows how a notion of objective
external world, looking very much like our own, can provably emerge from a
starting point in which the first-person perspective is primary, without
apriori assumptions on the existence of "laws" or a "physical world". While the
ideas here are perfectly compatible with physics as we know it, they imply some
quite surprising predictions and suggest that we may want to substantially
revise the way we think about some foundational questions.
