ABSTRACT
In his Introduction à l’épistémologie génétique-which has not yet been translated into English-Piaget (1950) maintained that the scientic method prohibits psychologists from choosing among the classic metaphysical solutions to the mind-body problem (e.g., interactionism, epiphenomenalism, idealism, and monism). Instead, Piaget argued, the solution to the mind-body problem must be found in the principle of psychophysical parallelism, which unites mental implication (e.g., the truth . . . of 2 + 2 = 4 ‘implies’ that of 4 – 2 = 2) and physical causality (e.g., a cannon causes the movement of two billiard balls; Piaget, 1963/1968, pp. 187-188). While other solutions entail either a privileging of causality (e.g., interactionism, epiphenomenalism) or a privileging of implication (e.g., idealism, monism), psychophysical parallelism unites the two in a nondichotomous relational matrix.
