  Already 71 years ago Rosenblueth, Wiener, and Bigelow introduced the concept
of the "behavioristic study of natural events" and proposed a classification of
systems according to the quality of the behaviors they are able to exercise. In
this paper we consider the problem of the resilience of a system when deployed
in a changing environment, which we tackle by considering the behaviors both
the system organs and the environment mutually exercise. We then introduce a
partial order and a metric space for those behaviors, and we use them to define
a behavioral interpretation of the concept of system-environment fit. Moreover
we suggest that behaviors based on the extrapolation of future environmental
requirements would allow systems to proactively improve their own
system-environment fit and optimally evolve their resilience. Finally we
describe how we plan to express a complex optimization strategy in terms of the
concepts introduced in this paper.
