 The picture that is at the core of Prior’s theory of branching time is reminiscent of the one evoked by Borges’ The Garden of Forking Paths. The interrelation of time and modality is represented as a tree of alternative histories that is linear towards the past and branches into multiple possible futures. Backward-linearity captures the idea that the past is fixed; forward-branching reflects the openness of the future. At each point in time, there may be more than one path leading towards the future, and each such path represents a future possibility.