“…[20,Example 2.11]) and its submonads, the filter monad and the ultrafilter monad in particular, are among the fundamental constructions of sets and play important roles in category theory, algebra, topology, and other disciplines, see e.g. [13,18,20,21]. Since the Goguen category Set(L) is not a topos unless L is a singleton set, its behavior is quite different to the category of sets when "powerobjects" are concerned [27].…”