Free What is Life?:How chemistry becomes biology by Addy Pross Page A

make, between the comfortable path of continuing to follow molecular biology’s lead or the more invigorating one of seeking a new and inspiring vision of the living world, one that addresses the major problems in biology that 20th centurybiology, molecular biology, could not handle and, so, avoided. The former course, though highly productive, is certain to turn biology into an engineering discipline. The latter holds the promise of making biology an even more fundamental science, one that, along with physics, probes and defines the nature of reality. 1
     
    Powerful and provocative words indeed. But in a sharp critique of holism, the Nobel biologist, Sydney Brenner, recently wrote: ‘The new science of systems biology claims to be able to solve the problem but I contend that this approach will fail because deducing models of function from the behaviour of a complex system is an inverse problem that is impossible to solve.’ 23
    Despite that treacherously uncertain backdrop, let us now briefly venture into this philosophic lion’s den. I will offer some thoughts on this troublesome philosophic divide and how it impacts on our goal of better understanding living systems. At least in the context of life, I propose that the reductionist–holistic divide is more semantic than substantive, and that holism, when probed more deeply, can be thought of as just a more elaborate form of reduction.
    At the risk of gross oversimplification we may state that the most useful application of reductionist philosophy, when viewed as a scientific methodology, is the one termed ‘hierarchical reduction’, the idea being that phenomena at one hierarchical level can be explained using concepts taken from a lower hierarchical level. Steven Weinberg recently expressed the idea succinctly: ‘explanatory arrows always point downward’. 24 Thus, to illustrate, one attempts to explain social behaviour based on individual organismic behaviour, organismic behaviour in terms of cellular behaviour, cellular behaviour based on biochemical cycles, and biochemical cycles rest upon more basic physical and chemical concepts ofmolecular structure and reactivity, and so on, continuing down to fundamental subatomic particles. Hierarchical reduction seeks to provide understanding level by level, with phenomena at each level being explained by the conceptual framework associated with the level immediately below. Much of the spectacular advance witnessed in the physical sciences since the scientific revolution of the seventeenth century can be directly attributed to the successful implementation of that methodology. Within the biological sciences, the reductionist harvest has been particularly abundant. The enormous advances in our understanding of biological processes, such as DNA replication, protein synthesis, metabolic cycles, etc., all derive from the reductionist methodology. Without question molecular biology has revealed many of the wonders of cell function at the molecular level—reduction
par excellence.
    But, as noted in chapter 1 , the enormous complexity of biological systems often makes the reductionist methodology difficult to implement, and it is that difficulty that has been responsible for the burgeoning anti-reductionist, holistic approach to biological systems of recent decades. The holistic view derives its persuasive influence from the
systems theory
school of thought that builds on the idea that within complex systems, systemic relations arise that produce novel and quite unpredictable characteristics. So, in recalling Weinberg’s reductionist comment ‘explanatory arrows always point downward’, together with June Goodfield’s despairing commentary, how are we to respond to the two opposing viewpoints? And what are the implications of this apparently fundamental disagreement with respect to our attempts to understand life?
    To a large extent criticism of the reductionist approach derives from extreme expressions of reduction, such