Abstract
Karen Neander’s (1991a, b) Selected Effects (SE) theory of biological proper functions argues that the function of a trait is the action for which it was “caused” to be selected by natural selection. Her life’s work has already left a lasting impact, however SE theory has yet to be more properly formalized as a conceptual analysis of biological functions. Although other SE theories have sought to build upon Neander’s work (e.g., Garson, 2017), there remains an ambiguity in the theory’s use of causal descriptors. For the success of her successors, delineating the function of causality for SE theory is of utmost importance. Here, I systematize Neander’s theory according to the different senses of causation inherent to it. I argue that structuring SE theory in terms of causal transitivity and intransitivity reveals that Neander’s analysis not only supersedes her detractors but likely exposes areas of vulnerability in others’ SE theory derivatives.