Thus, any Markov blanketed system will embody recurrent processes of autopoietic self-generation, which—as long as the system exists—enforces a difference between a living system and everything else [
33]. This means that these processes are fundamentally processes of identity constitution, given that they result in a functionally coherent unit [
36]. Casting operational closure in terms of the presence of a Markov blanket gives the notion of operational closure a statistical formulation. One of the nice things about casting operational closure in terms of the presence of a Markov blanket is that it allows us to explain what Varela [
36] called ‘the intriguing paradox’ of an autonomous identity: how a living system must both distinguish itself from its environment and, at the same time, maintain its energetic coupling to its environment to remain alive. According to Varela: ‘this linkage cannot be detached since it is against this very environment from which the organism arises, comes forth’ [
36, p. 78].
The answer to this apparent paradox lies in the conditional independencies induced by the presence of a Markov blanket, which (as we know) separates internal states and external states, and can be further decomposed into active states and internal states. Crucially, active and sensory states are distinguished in the following sense: active states influence but cannot be influenced by external states, while sensory states influence but cannot be influenced by internal states. This constraint enforces conditional independence between internal and external states—from which an autonomous identity can be shown to emerge—while creating a coupling between organism and environment via sensory and active states.