Thermodynamics, information and life revisited, Part II: 'Thermoeconomics'and 'control information'

In Part I of this paper, we critiqued the misuse of key concepts from therm odynamics acid information theory in various disciplines, but especially in relation to theories of biological evolution. Following a brief introducti on to this challenging literature, we began by drawing a critically importa nt distinction between 'order' and the informed 'functional organization' t hat characterizes living systems. We then outlined what we believe is the a ppropriate paradigm for theorizing about the role of energy and information in biological processes; in essence, our paradigm is cybernetic. This was followed by a brief discussion of thermodynamics, with particular reference to its application to biological processes. Two concepts that are well dev eloped in the engineering literature but not commonly used elsewhere provid e an approach that we believe is both more rigorous and more readily unders tood, namely the 'control volume' frame of reference and the concept of 'av ailable energy'. Both of these concepts were defined in precise mathematica l terms. In Part II, we discuss what we call the 'thermoeconomics' of livin g systems - that is, a cybernetic and economic approach to analyzing the ro le of available energy in biological evolution - and we relate this paradig m to a distinction that we draw between various statistical and structural definitions of information and what we call 'control information'. We criti que information theory and we define control information in cybernetic term s not as a 'thing' but as an attribute of the relationships between things - namely, the capacity (know-how,) to control the acquisition, disposition and utilization of matter/energy in purposive (teleonomic) processes. We al so suggest how control information can be measured empirically, and we prop ose a methodology for linking thermodynamics and information theory that co ntrasts sharply with existing approaches to this problem. Finally, we argue that irm living systems thermodynamic processes may be subject to certain law-like 'bioeconomic' principles. We also elucidate some implications. (C) 1998 John Wiley & Sons, Ltd.