Learning from water: Two complementary defi nitions of the concept of life

Abstract

The concept of life is central to biology and related life sciences, but there is no convergence on a defi nition. With the aim to resolve this problem analogies were studied between defi nitions of water and life. The concept of water refers to two phenomena: material particles (the H 2 O molecules) and interacting water molecules (liquid water). Likewise, the concept of life can be viewed as referring to a property of special material particles (the organisms) and to the system of interacting organisms (the ecosystem). In a comparable way as chemical theory has solved the problem of defi ning the water molecule, one can apply the Operator Theory for solving the problem of defi ning the organism concept. The analogy with water subsequently offers inspiration for two ontologically distinct defi nitions of life: (1) a defi nition of life as a general indication for a property that all organisms have, and (2) a defi nition of life that refers to a system of interacting organisms. These two defi nitions refer to different ontological kinds and accordingly cannot be merged into a single defi nition. For this reason the concept of life can be viewed as involving two, complementary, defi nitions. It is discussed how fi ndings based on the water-life analogy contribute to current discussions about the defi nition of life.