  The causal closure of physics is usually discussed in a context free way.
Here I discuss it in the context of engineering systems and biology, where
strong emergence takes place due to a combination of upwards emergence and
downwards causation [Ellis 2020]. Firstly, I show that causal closure is
strictly limited in terms of spatial interactions because these are cases that
are of necessity strongly interacting with the environment. Effective Spatial
Closure holds ceteris parabus, and can be violated by Black Swan Events.
Secondly, I show that causal closure in the hierarchy of emergence is a
strictly interlevel affair, and in the cases of engineering and biology
encompasses all levels from the social level to the particle physics level.
However Effective Causal Closure can usefully be defined for a restricted set
of levels, and one can experimentally determine Effective Theories that hold at
each level. This does not however imply those effective theories are causally
complete by themselves. In particular, the particle physics level is not
causally complete by itself in the contexts of solid state physics (because of
interlevel wave-particle duality), digital computers (where algorithms
determine outcomes), or biology (because of time dependent constraints).
Furthermore Inextricably Intertwined Levels occur in all these contexts.
