Intentionality

   The Problem of the Causal Efficacy of Intentionality

   Mental states are both caused by the operations of the brain and realized in the structure of the brain (and the rest of the central nervous system). Once the possibility of mental and physical phenomena standing in both these relations is understood we have removed at least one major obstacle to seeing how mental states which are caused by brain states can also cause further brain states and mental states.

   But this model of "caused by" and "realized in" only raises the next question, how can Intentionality function causally? Granted that Intentional states can themselves be caused by and realized in the structure of the brain, how can Intentionality itself have any causal efficacy? When I raise my arm my intention in action causes my arm to go up. This is a case of a mental event causing a physical event. But, one might ask, how could such a thing occur? My arm going up is caused entirely by a series of neuron firings. We do not know where in the brain these firings originate, but they go at some point through the motor cortex and control a series of arm muscles which contract when the appropriate neurons fire. Now what has any mental event got to do with all of this? As with our previous questions, I want to answer this one by appealing to different levels of description of a substance, where the phenomena at each of the different levels function causally. (Searle, 1983, pp. 265, 268)