Heylighen, Francis and Joslyn, Cliff: (1993) ``Systems Theory'', in:
Cambridge Dictionary of Philosophy, ed. R. Audi, Cambridge U. Press,
Cambridge MA, to appear
Systems Theory [Including Systems Analysis]: the transdisci-
plinary study of the abstract ORGANIZATION of phenomena, in-
dependent of their substance, type, or spatial or temporal scale of
existence. It investigates both the principles common to all com-
plex entities, and the (usually mathematical) MODELS which can
be used to describe them.
Systems theory was proposed in the 1940's by the biologist Lud-
wig von Bertalanfy (anthology: General Systems Theory, 1968),
and furthered by Ross Ashby (Introduction to Cybernetics, 1956).
von Bertlanffy was both reacting against REDUCTIONISM and at-
tempting to revive the UNITY OF SCIENCE. He emphasized that
real systems are open to, and interact with, their environments, and
that they can acquire qualitatively new properties through EMER-
GENCE, resulting in continual EVOLUTION. Rather than reducing
an entity (e.g. the human body) to the properties of its parts or el-
ements (e.g. organs or cells), systems theory focuses on the arrange-
ment of and RELATIONS between the parts which connect them into
a whole (cf. HOLISM). This particular ORGANIZATION determines
a SYSTEM, which is independent of the concrete substance of the el-
ements (e.g. particles, cells, transistors, people, etc). Thus, the same
concepts and principles of organization underlie the different disci-
plines (physics, biology, technology, sociology, etc.), providing a basis
for their unification. Systems concepts include: system-environment
BOUNDARY, INPUT, OUTPUT, PROCESS, STATE, HIERAR-
CHY, GOAL-DIRECTEDNESS, and INFORMATION.
The developments of systems theory are diverse (Klir, Facets of
Systems Science, 1991), including conceptual foundations and phi-
losophy (e.g. the philosophies of Bunge, Bahm and Laszlo); math-
ematical modeling and INFORMATION THEORY (e.g. the work
of Mesarovic and Klir); and practical applications. Mathematical
systems theory arose from the development of isomorphies between
the models of electrical circuits and other systems. Applications
include engineering, computing, ecology, management, and family
psychotherapy. Systems analysis, developed independently of sys-
tems theory, applies systems principles to aid a decision-maker with
problems of identifying, reconstructing, optimizing, and controlling
a system (usually a socio-technical organization), while taking into
account multiple objectives, constraints and resources. It aims to
specify possible courses of action, together with their risks, costs
and benefits. Systems theory is closely connected to CYBERNET-
ICS, and also to SYSTEM DYNAMICS, which models changes in a
NETWORK of coupled variables (e.g. the "world dynamics" mod-
els of Jay Forrester and the Club of Rome). Related ideas are
used in the emerging "sciences of COMPLEXITY", studying SELF-
ORGANIZATION and heterogeneous networks of interacting actors,
and associated domains such as FAR-FROM-EQUILIBRIUM THER-
MODYNAMICS, CHAOTIC DYNAMICS, ARTIFICIAL LIFE, AR-
TIFICIAL INTELLIGENCE, NEURAL NETWORKS, and computer
MODELING AND SIMULATION.