Causal Exclusion

"Causal analysis as presented
here endorses both supervenience (no extra causal ingredients at
the macro level) and causal exclusion [for a given system at
a given time, causation occurs at one level only, otherwise causes
would be double counted (4)]. However, causal analysis also
demonstrates that EI can actually be maximal at a macro level,
depending on the system’s architecture. In such cases, causal exclusion
turns the reductionist assumption on its head, because to
avoid double-counting causes, optimal macro causation must
exclude micro causation. In other words, macro mechanisms can
always be decomposed to their constituting micro mechanisms
(supervenience); however, if there is emergence, macro causation
does not reduce to micro causation, in which case the macro wins
causally against the micro and takes its place (supersedence). The
notion of irreducibility among levels (does the macro beat the
micro?) is complemented by the notion of irreducibility among
subsets of elements within a level [is the whole more than its
parts (15, 25)?]. From the perspective of a system, emergence
(CE > 0) implies causal “self-definition” at the optimal macro
level—the one at which its causal interactions “come into focus”
(30) and “the action happens.”"

Hoel, E.P. et al. 2013. Quantifying causal emergence shows that macro can beat micro. Proceedings of the National Academy of Sciences USA 110: 19790–19795.