  Because this research has received extensive treatment in recent work on free will, we will not consider it further, but instead refer interested readers to the sources cited above and to Mele 2014 for critical discussion and references. Here we simply note that traditional and contemporary attempts to assess the efficacy of mental states have run up against philosophical difficulties as well, difficulties that tend to overshadow the experimental evidence accumulated thus far. In this sense, the efficacy of mind is quite unlike that of, say, the moon or smoking. This will, we hope, become clear in the discussion to follow.