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 thermodynamics acid information theory in various disciplines, but especially in relation to theories of biological evolution. Following a brief introduction to this challenging literature, we began by drawing a critically important distinction between 'order' and the informed 'functional organization' that characterizes living systems. We then outlined what we believe is the appropriate 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 developed in the engineering literature but not commonly used elsewhere provide an approach that we believe is both more rigorous and more readily understood, namely the 'control volume' frame of reference and the concept of 'available energy'. Both of these concepts were defined in precise mathematical terms. In Part II, we discuss what we call the 'thermoeconomics' of living systems - that is, a cybernetic and economic approach to analyzing the role of available energy in biological evolution - and we relate this paradigm to a distinction that we draw between various statistical and structural definitions of information and what we call 'control information'. We critique information theory and we define control information in cybernetic terms 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 also suggest how control information can be measured empirically, and we propose a methodology for linking thermodynamics and information theory that contrasts 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.