In the last chapter, we saw that work on syllogistic reasoning contains several themes: (i) the formal description of the elements of the problems, (ii) the observation of human performance on those problems, (iii) the question of the extent to which human performance approaches or deviates from the norms established by the formal properties, and (iv) the kinds of explanation, from the particular to the general, that have been produced to account for this performance. These themes are common to all fields of reasoning research, and so will be continued in this chapter.