The Cartesian view of classical science had described the
world as an automaton, which was deterministic and capable of
total description in the form of causal laws, or "laws of nature."
Today many natural scientists would argue that the world should
be described quite differently. 9 It is a more unstable world, a
much more complex world, a world in which perturbations play
a big role, one of whose key questions is how to explain how such
complexity arises. Most natural scientists no longer believe that
the macroscopic can simply be deduced in principle from a simpler microscopic world. Many now believe that complex systems
are self-organizing, and that consequently nature can no longer
be considered to be passive.
It is not that they believe Newtonian physics to be wrong, but
that the stable, time-reversible systems which Newtonian science described represent only a special, limited segment of reality. Newtonian physics describes, for example, the motion of
the planets but not the development of the planetary system. It
describes systems at equilibrium or near to equilibrium but not
systems far from equilibrium, conditions that are at least as
frequent, if not more frequent, than systems at equilibrium.
The conditions of a system far from equilibrium are not timereversible, in which it is sufficient to know the "law" and the initial conditions in order to predict its future states. Rather, a system far from equilibrium is the expression of an "arrow of time,"
whose role is essential and constructive. In such a system, the future is uncertain and the conditions are irreversible. The laws
that we can formulate therefore enumerate only possibilities,
never certainties.