We propose a conceptual and formal characterisation of biological organisation as a closure of constraints. We first establish a distinction between two causal regimes at work in biological systems: processes, which refer to the whole set of changes occurring in non-equilibrium open thermodynamic conditions, and constraints, those entities which, while acting upon the processes, exhibit some form of conservation (symmetry) at the relevant time scales. We then argue that, in biological systems, constraints realise closure, i.e. mutual dependence such that they both depend on and contribute to maintaining each other. With this characterisation in hand, we discuss how organisational closure can provide an operational tool for marking the boundaries between interacting biological systems. We conclude by focusing on the original conception of the relationship between stability and variation which emerges from this framework. – Highlights:Biological systems realise both organisational closure and thermodynamic openness, Organisational closure is a closure of constraints, Constraints exhibit conservation (symmetry) at the relevant time scales, Closure draws the boundaries between interacting biological systems, Closure is a principle of biological stabilisation.

Key words: Biological organisation, Closure, Constraints, Symmetries, Time scales

This book presents a mathematical analysis of explanations. A valid explanation must be self-consistent, and the expectations it generates must be valid. Beyond this, the correctness of any ontology defined by an explanation cannot be investigated. The analysis does not operate with speculative arguments about reality. Instead, it defines a fully general framework where the logical consequences of mere self-consistency can be analyzed. Self-consistency implies symmetries which can be mathematically expressed. That expression is true for any self-consistent explanation, and it also stands only a few algebraic steps away from the relationships of quantum mechanics, electromagnetism and special relativity. General relativity also arises as an approximated solution, from a framework that is fully consistent with quantum mechanics. The fact that modern physics can be deduced this way implies that physics is not so much about reality as it is about valid mental representations of expectations of reality. The algebraic steps in the analysis represent arbitrary terminology choices, and the rest falls out from self-consistency alone. Expectations can always be expressed in a form where the data is categorized to look like modern physics. Also it is shown that the same expectations can always be expressed in many different but equally valid forms. Relevance: The book deals with epistemological questions on a constructivist background and portrays “ontological claims,” i.e., claims about actual reality as undefendable (belief based) and thus meaningless.