  We study local activity and its opposite, local passivity, for linear systems
and show that generically an eigenvalue of the system matrix with positive real
part implies local activity. If all state variables are port variables we prove
that the system is locally active if and only if the system matrix is not
dissipative. Local activity was suggested by Leon Chua as an indicator for the
emergence of complexity of nonlinear systems. We propose an abstract scheme
which indicates how local activity could be applied to nonlinear systems and
list open questions about possible consequences for complexity.
