Following von Wright, ``transitions'' are needed for understanding agency. I indicate how von Wright's account of transitions should be adapted to take account of objective indeterminism, using the idea of branching space-time. The essential point is the need to locate transitions not merely in space-time, but concretely amid the indeterministic, causally structured possibilities of our (only) world. (This is a ``postprint'' of Belnap 1999, as cited in the paper. The page numbers do not, of course, match those of the original.).

``Branching space-time'' is a simple blend of relativity and indeterminism. Postulates and definitions rigorously describe the ``causal order'' relation between possible point events. The key postulate is a version of ``everything has a causal origin''; key defined terms include ``history'' and ``choice point.'' Some elementary but helpful facts are proved. Application is made to the status of causal contemporaries of indeterministic events, to how ``splitting'' of histories happens, to indeterminism without choice, and to Einstein-Podolsky-Rosen distant correlations.