Systems are mental constructs.
They're defined by boundaries.
The boundary of the system,
the boundary of things we declare to be parts of the system,
the boundaries of the concepts we use
to construct, communicate, and reason about the system.
The words "system" and "boundary" can be misleading,
like the word "process."
As if nature contains conceptual abstractions.
Abstractions happen in cognition.
Nowhere else.
But did you notice the choice, there,
to place cognition outside of nature?
Is that where it belongs?
How would we know?
Questioning and evaluating boundaries
can press this question relentlessly.