We may gain a clearer perspective on the mind-brain identity conundrum if we do not immediately entangle ourselves in technical rninutT"ae and partisan bickering. Here is what seems to me a basic and quite challenging riddle in this area: We cannot deny that some conditions of our body have a great deal to do with our mental activities and capacities. Ancient physicians, as well as ordinary folk, realized that when a person sustains head injuries, contracts a high fever, stays out too long under hot sunlight, or ingests certain drugs and fermented liquors, very often her or his behavior and thinking change dramatically. Recent neurophysiologists have expanded the list of material circumstances which seem to have a bearing upon our memories, skills, beliefs, moods, desires, dreams and so forth. Most important of all, contemporary researchers have demonstrated the ubiquitous and vital role that our nervous system plays in avast range of our normal and our defective or aberrant psychological states.
How should we, as philosophers attempting to understand human mentality, go about interpreting these humdrum and arcane facts? A very natural account would be that some bodily, and in particular some neural happenings, causally determine our state of mind: they must be at least causally necessary, or 'standing', conditions of it; possibly they are also sufficient to bring it about. And if these physical occurrences affect our mind, there is no reason why our mental state -our pain, our worry, especially our decision to actshould not in its turn influence our brain, and indirectly the rest of our body. So far so good. But this causal hypothesis has an interesting consequence. Assume that every neural happening which concerns us is either a cause or an effect of our mental state. Then that state must be distinct from every such cause or effect. Accordingly, the mental state in question cannot itself be a neural event. It is what results from, or propagates, various cerebral going-on. Nor can the mental occurrence be an event elsewhere in our body -for example, the flow of gastric juices in our stomach.