  This entry reflects the influence of all of these sources.  To be sure, we shall see the main results on the set theory obtained using AFA.  Also, we present enough of the theory that someone who needs to read papers that use it should be able to do start doing so. We also emphasize the conceptual underpinnings of the subject, and compare them to more standard foundational work.  This is hardly ever done in technical papers on the subject, but should be of interest to people in several areas of philosophy.  Finally, our work incorporates many ideas and results coming from the coalgebra research community in the years following the publication of Aczel 1988.