Defining life: an exercise in semantics or a route to biological insights?

Asking ‘What is X?’ questions is a natural human inclination, and because all scientists that have so far published are undoubtedly human, they discuss such issues often enough. ‘What is Life?’ almost by definition is the king of such questions as far as Biology is concerned (1). Indeed, in the article which I address in this commentary (2), Edward Trifonov cites a recent special issue of the journal Origins of Life and Evolution of Biospheres that consists of 16 articles fully dedicated to different aspects of defining Life and the features of the resulting definitions (3). Certainly, this is evidence of considerable attention to the subject. Yet, in itself the question ‘What is Life?’ hardly can be considered scientific. Falsification is impossible: whenever one finds an apparent counterexample, i.e. an entity that possesses all attributes included in the given definition that, however, is “clearly” not alive or conversely, an entity that lacks some of those attributes but is “obviously” a life form, some kind of intuitive understanding of the living state superseding any definition is involved. Even corroboration of a definition of life that would involve finding more and more diverse entities fitting the definition is compromised by the same problem: to count a case as supportive, an independent criterion is required, but this can only be intuitive.