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

as the one offered by FrancisCrick, 25 who claimed that ‘the ultimate aim of the modern movement in biology is to explain all biology in terms of physics and chemistry’. Such claims appear unrealistic for the foreseeable future, and remain an ultimate aim in just the same way that the ‘ultimate aim’ of chemistry is to predict all chemical phenomena through solving Schrödinger’s famous wave equation. In that sense the broadly based critique of reduction, given its inherent limitations, is on solid ground. But the idea that a more measured reductionist approach is unable to deal with emergent properties at all is clearly incorrect; emergent properties are regularly addressed and understood through reduction.
    To take a simple example, consider the physical properties of condensed states (that’s just the term for solids and liquids) that we discussed earlier. Condensed states exhibit a variety of emergent properties that are totally absent at the single molecule level. The condensed state may be solid or liquid, it may be conducting or insulating, shiny or dull. A single molecule does not possess any of those condensed state properties. A single molecule is neither solid, nor liquid, neither shiny nor dull. Nonetheless, despite the absence of these collective properties at the molecular level, these condensed state properties are well understood based on the electronic characteristics of the
individual
molecules. So we understand why at room temperature molecular hydrogen is a gas, water is a liquid, and regular table salt is a solid, based solely on properties of the individual molecules (molecular weight, charge character, etc.) and the corresponding intermolecular forces that would be expected in those materials. Similarly we may usefully predict the solid state conductivity of a material by carrying out a particular kind of theoretical analysis on the
individual
isolated molecule.
    My point is that physics and chemistry are replete with such reductionist analyses that offer insight into the underlying reasons for a wide range of emergent properties. The oft cited claim that some properties cannot be explained by reduction because they are emergent is simply incorrect, though, of course, this does not mean that
all
emergent properties can be explained by reduction. Reduction as a methodology does have its limitations, as does any methodology. Complex systems cannot always be readily reduced to their component parts. Unexpected emergent properties can and do appear and in those cases, it could be argued, a holistic approach may be necessary. But a deeper appraisal of the holistic view suggests that its anti-reductionist claim is misstated to a degree. The problem lies primarily with the meaning that the term ‘holistic’ conveys. If ‘holistic’ is intended to convey the impression that the entire system is treated as a whole entity, that reduction into components is avoided, then that is certainly not the case. The systems approach dissects the complex whole into component parts as does the reductionist approach, but addresses the complex nature of interactions within the system in a more realistic fashion. The holistic view recognizes that in addition to ‘upward causation’ from lower-level hierarchies to higher ones, one must also consider the possibility of ‘downward causation’ where higher-level phenomena influence actions at lower levels.
    These kinds of feedback effects can lead to quite unexpected emergent properties that cannot be easily foreseen and are not readily amenable to a simple reductionist analysis. Nonetheless a moment’s thought reveals that a reductionist philosophy is at the heart of holism as well. The holistic systems approach to understanding the complexity of a biological system continues to reduce the complex system intosimpler elements, though placing greater emphasis on the complex nature of the interactions between those elements. In other words the holistic approach