The issue of "closure" in Jagers op Akkerhuis's operator theory.

Attempts to define life should focus on the transition from molecules to cells and the "closure" aspects of this event. Rather than classifying existing objects into living and non-living entities I believe the challenge is to understand how the transition from non-life to life can take place, that is, the how the closure in Jagers op Akkerhuis's hierarchical classification of operators, comes about. © 2010 Springer Science+Business Media B.V