  Moore wrote more extensively about perception than about any other topic. In these writings he moves between the three alternatives set out here without coming to any firm conclusion. From the outside, it seems clear that what was leading him astray was the sense-datum hypothesis itself and his reflections on perception can be regarded as an extended reductio ad absurdum of this hypothesis. It was only towards the end of his career that he encountered in Ducasse's adverbial theory a serious alternative to the sense-datum hypothesis. But the adverbial theory provides no easy way of avoiding the difficulties Moore confronted: Moore rightly objected to Ducasse that it is not at all clear how the structure of a sensory field can be construed in adverbial terms. Yet there were other alternatives: in particular, from the start of the twentieth century the phenomenological movement had offered an account of perception based upon a recognition of its inherent intentionality which avoids some of the pitfalls of the sense-datum theory. It is, I think, a pity that Moore did not engage with this position, but this detachment was all too characteristic of the relationship at the time between the analytical and phenomenological traditions.