The goal of synthetic biology is to create artificial organisms. To achieve this it is essential to understand what life is. Metabolism-replacement systems, or (M, R)-systems, constitute a theory of life developed by Robert Rosen, characterized in the statement that organisms are closed to efficient causation, which means that they must themselves produce all the catalysts they need. This theory overlaps in part with other current theories, including autopoiesis, the chemoton, and autocatalytic sets, all of them invoking some idea (...) of closure. A simple model of an (M, R)-system has been implemented in the computer, and behaves in ways that may shed light on the requirements for a prebiotic self-organizing system. In addition to a trivial steady state in which nothing happens, it can establish a non-trivial steady state in which all intermediates have finite concentrations, with their rates of degradation balanced by their rates of synthesis. The system can be regenerated from the set of food components plus a single intermediate, and maintain itself in that state indefinitely, despite continuous degradation. At the very low compartment volumes that may have existed in prebiotic conditions, for example in cavities in minerals, or in micelles formed by simple amphiphiles, statistical fluctuations in the numbers of molecules need to be taken into account. With the stochastic approach there is no non-trivial steady state in strict mathematical terms, because the system will always collapse to the trivial state after sufficient time. However, the average time before collapse is so long for volumes greater than $10^{-19}\;{\textsc{l}}$ (much smaller than the volume of the order of $10^{-15}\;{\textsc{l}}$ for a typical bacterial cell) that for practical purposes the self-maintaining state of non-null concentrations becomes significant, recalling the situation of bistability that is observed in deterministic analysis. In turn, there exists a minimum size below which the self-organizing system cannot maintain itself on chemically relevant time scales. The value of the critical volume depends on the particular concentrations and rate constants assumed, but the principle could apply generally. (shrink)

This paper examines three exemplary theories of living organization with respect to their common feature of defining life in terms of metabolic closure: autopoiesis, (M, R) systems, and chemoton theory. Metabolic closure is broadly understood to denote the property of organized chemical systems that each component necessary for the maintenance of the system is produced from within the system itself, except for an input of energy. It is argued that two of the theories considered—autopoiesis and (M, R) systems—participate in (...) a hylomorphist pattern of thinking which separates the “form” of the living system from its “matter.” The analysis and critique of hylomorphism found in the work of the philosopher Gilbert Simondon is then applied to these two theories, and on the basis of this critique it is argued that the chemoton model offers a superior theory of minimal life which overcomes many of the problems associated with the other two. Throughout, the relationship between hylomorphism and the understanding of living things as machines is explored. The paper concludes by considering how hylomorphism as a background ontology for theories of life fundamentally influences the way life is defined. (shrink)

Mechanistic explanation is the dominant approach to explanation in the life sciences, but it has been challenged as incompatible with a conception of humans as agents whose capacity for self-direction endows them with freedom and dignity. We argue that the mechanical philosophy, properly construed, has sufficient resources to explain how such characteristics can arise in a material world. Biological mechanisms must be regarded as active, not only reactive, and as organized so as to maintain themselves far from thermodynamic equilibrium. Notions (...) from systems biology make key contributions, particularly Gánti’s chemoton, Ruiz-Mirazo and Moreno’s basic autonomy, and Barandiaran and Moreno’s adaptive autonomous agents. The reconstrual is then extended to mental life by conceiving of cognitive mechanisms as control components in inherently active systems, as illustrated in models offered by Randall Beer and Cees van Leeuwen. (shrink)

Mechanistic explanation is the dominant approach to explanation in the life sciences, but it has been challenged as incompatible with a conception of humans as agents whose capacity for self-direction endows them with freedom and dignity. We argue that the mechanical philosophy, properly construed, has sufficient resources to explain how such characteristics can arise in a material world. Biological mechanisms must be regarded as active, not only reactive, and as organized so as to maintain themselves far from thermodynamic equilibrium. Notions (...) from systems biology make key contributions, particularly Gánti’s chemoton, Ruiz-Mirazo and Moreno’s basic autonomy, and Barandiaran and Moreno’s adaptive autonomous agents. The reconstrual is then extended to mental life by conceiving of cognitive mechanisms as control components in inherently active systems, as illustrated in models offered by Randall Beer and Cees van Leeuwen. (shrink)