  If a concept is not well defined, there are grounds for its abuse. This is
particularly true of complexity, an inherently interdisciplinary concept that
has penetrated very different fields of intellectual activity from physics to
linguistics, but with no underlying, unified theory. Complexity has become a
popular buzzword used in the hope of gaining attention or funding -- institutes
and research networks associated with complex systems grow like mushrooms. Why
and how did it happen that this vague notion has become a central motif in
modern science? Is it only a fashion, a kind of sociological phenomenon, or is
it a sign of a changing paradigm of our perception of the laws of nature and of
the approaches required to understand them? Because virtually every real system
is inherently extremely complicated, to say that a system is complex is almost
an empty statement - couldn't an Institute of Complex Systems just as well be
called an Institute for Almost Everything? Despite these valid concerns, the
world is indeed made of many highly interconnected parts over many scales,
whose interactions result in a complex behaviour needing separate
interpretation for each level. This realization forces us to appreciate that
new features emerge as one goes from one scale to another, so it follows that
the science of complexity is about revealing the principles governing the ways
by which these new properties appear.
