Horizontal and Vertical Determination of Mental and Neural States

Mental and neural states are related to one another by vertical (synchronic) interlevel relations and by horizontal (diachronic) intralevel relations. For particular choices of such relations, problems arise if causal efficacy is ascribed to mental states. In a series of influential papers and books, Kim has presented his much discussed “supervenience argument”, which ultimately amounts to the dilemma that mental states either are causally inefficacious or they hold the threat of overdetermining neural states. Forced by this disjunction, Kim votes in favor of overdetermination and, ultimately, reduction. We propose a perspective on mental causation that dissolves the assumption of a tension between horizontal and vertical determination. For mental states to be causally efficacious, they must be dynamically stable. This important requirement can be implemented by combining a key idea of supervenience, multiple realization, with the recently introduced vertical interlevel relation of contextual emergence. Both together deflate Kim’s dilemma and reflate the causal efficacy of mental states.