 One approach here would be to attempt to define life, or living agent, or to provide necessary and sufficient conditions for these (Maynard Smith &amp; Szathmáry 1995: 17–18; Cleland 2012). A recurrent property in such definitions is that of having a metabolism, which involves both an anabolic dimension in the breakdown of chemical molecules to produce energy and a catabolic dimension in intracellular synthesis of those compounds (Pradeu 2016b: 801). But there are other properties that living agents have, some presupposed by that of having a metabolism, others existing independently. These include what might be thought of as structural properties—such as having heterogeneous and specialized parts, including a variety of internal mechanisms, and containing diverse organic molecules, including nucleic acids and proteins—as well as functional or dispositional properties—such as the capacity for growth or development, reproduction, and self-repair.