In pursuit of the Galois group.
Shelah defined the space SSh(T) of strong types of a first order theory T. A profinite Galois group acts on this space; the quotient is the space of types S(T). For a stable theory, Shelah showed that SSh is the gateway to all analysis of interactions between substructures of models of T.
Lascar in 1982 undertook a generalization to arbitrary theories. As later clarified, the space SKP of Kim-Pillay types can be defined; a compact group G∗ acts on SKP, with quotient S(T). For simple theories, or ones with a definable measure, an excellent theory of amalgamation becomes possible.
For arbitrary theories, the investigation continued at the hands of Newelski, Krupinski, Rzepecki, Pillay, and others; a new compact group was found by means of a journey to topological dynamics. I will recount some of this story, and describe a more finitary compact group, that arises as the automorphism group of a new space generalizing SKP, the pattern space of T. The elements of the quotient space here are not the types but the maximal elements of the Lascar-Poizat fundamental order.