Final answer:
Jean-Paul Sartre refers to the unchangeable events of our past as our facticity, which sets the boundaries of human freedom. Sartre's existentialist philosophy emphasizes our responsibility within these boundaries, underpinning the belief that existence precedes essence.
Step-by-step explanation:
Jean-Paul Sartre refers to those events in our past that we cannot change as our facticity. Facticity encompasses all of the concrete details against the background of which human freedom exists and is limited. This concept is opposed to transcendence, which refers to the spontaneous acts and projections that go beyond these given facts of our existence. This is central to Sartre's existential philosophy where he emphasizes that while our facticity is a boundary of our freedom, we remain responsible for how we shape our lives within these limits. An understanding of our facticity is vital to understanding the core existentialist belief that "existence precedes essence," which means that one's existence comes before any predefined purpose or essence.