Assigning biological functions: making sense of causal chains

A meaningful distinction can be made between functions and mere effects in biological systems without resorting to teleological arguments: (i) biological systems must cope with a multitude of problems or they will cease to exist; (ii) the solutions to these problems invariably depend on circular causal chains (“feedback loops”); and (iii) biological functions are attributes of elements in biological systems that have an effect which, by contributing to the correcting behavior of a feedback control system, assists in solving a biological problem. The analysis is applied to several biological systems. The proposed solution is discussed primarily in its relation to two popular approaches to the concept of biological function, i.e., the “causal role accounts” and the “selected effect accounts”.