editorial changes not yet reviewed by author Purpose My intent in this essay is to reflect on the history of some biological notions such as autopoiesis, structural coupling, and cognition, that I have developed since the early 1960’s as a result of my work on visual perception and the organization of the living. No doubt I shall repeat things that I have said in other publications (Maturana and Varela 1980 and 1988), and I shall present notions that once they are (...) said appear as obvious truisms. But the reader it is not invited to attend to the truisms, rather he or she is invited to attend to the consequences that they entail for the understanding of biological processes. After all, explanations or demonstrations always become self evident once they are understood and accepted. KEYWORDS Autopoiesis, structural coupling, cognition, explanations, self consciousness, 1. Autopoiesis 1.1 Origins of the notion In November 1960, a first year medical student asked me the question “What began three thousand eight hundred million years ago so that you can say now that living systems began then?” I realized that I could not properly answer that question, so I said “I cannot answer this question now, but if you come back next year I shall propose an answer then.” Thus I accepted the question of the student to be answered later, and as I did so, I accepted also the question for myself. I realized that to answer this question I had to create a living system, either conceptually or practically, because I had to be able to say what kind of systems were living system to be able to say how they began. While in the attempting to answer the dual questions of what kind of systems are living systems, and of how did they begin so that I could now speak of their origin, it became obvious to me that living systems exist as autonomous entities in the form of self contained closed molecular dynamics of self production, open to the flow of molecules through them. Indeed, one can say that living systems arose in the history of the earth in the moment in which some spontaneous networks of molecular autocatalytic processes became closed upon themselves.. (shrink)