  Currently the two popular ways to practice Robinson's nonstandard analysis
are the model-theoretic approach and the axiomatic/syntactic approach. It is
sometimes claimed that the internal axiomatic approach is unable to handle
constructions relying on external sets. We show that internal frameworks
provide successful accounts of nonstandard hulls and Loeb measures. The basic
fact this work relies on is that the ultrapower of the standard universe by a
standard ultrafilter is naturally isomorphic to a subuniverse of the internal
universe.
