One of the issues addressed in this book regarded the ancient question of the definition of life. Ancient because it could have been asked at any time in the past; Renaissance people did not have to wait until Watson and Crick to deal intelligently with the question, “what is life?” Even so, we have seen a very broad spectrum of opinions. Not a surprise, since the quest for the origin of life provokes interest not only in life sciences (biology, chemistry, molecular biology, bioengineering, artificial life, and astrobiology) but also in philosophy and theology. Each one with its own language and traditions, and each group sticks to their own. No unifying view.

This may be so, but it does not mean that this is the way of good science. Good science should aim at a convergence towards a common denominator, and in the case of the question “what is life?,” it should converge towards what Sir Stafford Beer sees as “the understanding of the organization of the living systems in relation to their unitary character” (Beer, in Maturana and Varela, 1980, p. 65).

In this book, I have emphasized that a way to do so is to see life as a systems view: to see life as a confederacy of components that in virtue of their specific mutual interaction form a collective, organized unity. The systems view also includes the interaction with the environment in the specific niche.

I offered the full expression of the systems view of life in Part II of this book, with the description and reappraisal of the theory of autopoiesis. I believe that this theory has identified the common denominator of life in all living organisms. When we say, “the living is an open, self-maintaining molecular system due to self-regeneration of the components within a boundary of its own making,” we should recognize that there is no living system on our Earth that does not comply with such a statement. I also made the point that it is ontologically wrong to answer the question “what is life?” with the word reproduction. Reproduction is a property of life; it does not say anything about why and how an organism is alive. Reproduction is certainly the main mechanism and criterion of evolution and biodiversity, but not the criterion of life.