This classic introduction to Maturana's theory of autopoiesis contains two landmark essays: "Biology of Cognition" and "Autopoiesis".
Maturana argues that the relation with the environment molds the "configuration" of a cognitive system. Autopoiesis is the process by which an organism continously reorganizes its own structure. Adaptation consists in regenerating the organism's structure so that its relationship to the environment remains constant. An organism is therefore a structure capable to respond to the environment, and the stimulus is the part of environment that is absorbed by the structure.
Living systems are units of interaction. They only exist in an environment. They cannot be understood independently of their environment. They exhibit exergonic metabolism, which provides energy for endergonic synthesis of polymers, i.e. for growth and replication. The circular organization of living organisms constitutes a homeostatic system whose function is to maintain this very same circular organization. It is such circular organization that makes a living system a unit of interaction. At the same time it is this circular organization that helps maintain the organism's identity through its interactions with the environment. Due to this circular organization, a living system is a self-referring system.
Cognition is biological in the sense that the cognitive domain of an organism is defined by its interactions with the environment. A living system operates as an inductive system and in a predictive manner: its organization reflects regularities in the environment ("what happened once will occur again"). Living systems are cognitive systems. Living is a process of cognition. The internal state of a living organism is changed by a cognitive interaction in a way relevant to the circularity of its organization (to its identity). The nervous system enables a broader way to interact and eventually self-consciousness.
Maturana assumes that intelligent behavior originates in extremely simple processes: the living cell is nothing special, but many living cells one next to the other become a complex system thanks to autopoiesis.
An autopoietic system is a network of transformation and destruction processes whose components interact to continously regenerate the network An autopoietic system holds costant its organization (its identity). Autopoiesis generates a structural coupling with the environment: the structure of the nervous system of an organism generates patterns of activity that are triggered by perturbations from the environment and that contribute to the continuing autopoiesis of the organism. Autopoiesis is necessary and sufficient to characterize a living system.
All living systems are cognitive systems. Cognition is simply the process of maintaining itself by acting in the environment.
Language is connotative and not denotative. Its function is to orient the organism within its cognitive domain. Maturana extends the term "linguistic" to any mutually generated domain of interactions (any "consensual domain").
Maturana assumes that multi-cellular organisms are born when two or more autopoietic units engage in an interaction that takes place more often than any of the interactions of each unit with the rest of the environment (a "structural coupling"). Inert elements become macromoleculs, and macromolecules become organic cells, and so on towards cellular organisms and intelligent beings.
The structures that are effectively built are those that make sense in the environment.
Cognition is a purely biological phenomenon. Organisms do not use any representational structures, but their intelligent behavior is due only to the continous change in their nervous system as induced by perception. Intelligence is action. Memory is not an abstract entity but simply the ability to recreate the behavior that best couples with a recurring situation within the environment.
Even human society as a whole operates as a homeostatic system.
With these essays Maturana revolutionized the study of living organisms and laid a bridge between biological and cognitive studies. The "organism" became a component of the environment, that has no relevance by itself, and the "cognition" of an organism became just an aspect of the organism's interaction with the environment.