"existence precedes essence", which he understood as a repudiation of the philosophical system that had come before him. Instead of "is-ness" generating "actuality," he argued that existence and actuality come first, and the essence is derived afterward.

In this respect he breaks with Søren Kierkegaard, who, although often described as a proto-existentialist, identified essence as "nature." For him, there is no such thing as "human nature"