Shields, C. Synthese (2012) 185: 103. doi:10.1007/s11229-011-9878-8
In the dialectic of debates about the extension of life, one witnesses a predictably repeating pattern: one side appeals to a motley of variegated criteria for something’s qualifying as a living system, only to find an opposite side taking issue with the individual necessity or collective sufficiency of the proposed criteria. Some of these criteria tend to cluster with one another, while others do not: metabolism, growth and reproduction; self-organization and homeostasis; an ability to decrease internal entropy by the appropriation of free energy; stimulus response suited to self-preservation and propagation; and adaptation. In competing approaches to the extension of life, these sundry criteria thus jockey for authority, with one group of theorists promoting some subset of them as essential for life, where the appeal to essence is as likely as not to be a simple modal sine qua non, and another denying that the nominated criteria are really necessary at all. The debate then stalls, because there seems to be no shared methodology for adjudicating such disputes. We may address this unhappy situation successfully by coming to appreciate that life is what we may call a core-dependent homonym.