Existentialism, Individuation, Action

A definition of 'Existentialism' is as difficult to formulate as is one of 'existence'. On the other hand, one commonality to five Philosophers often considered to be the most prominent 'Existentialists'--Nietzsche, Kierkergaard, Heidegger, Jaspers, and Sartre--is a singular personal experience which serves each as a Principle of Individuation. For Nietzsche, it is the affirmation of Eternal Recurrence; for Kierkergaard, it is a 'leap of faith'; and, for Jaspers, it is the relationship with God. For Heidegger, according to Being and Time, it is Death, i. e. one's 'ownmost possibility', one's awareness of which detaches one from anonymous involvement in the 'they'. However, Sartre rejects this analysis of Death--since one can never experience one's own Death, there is nothing 'ownmost' about it, and, instead, it has meaning only anonymously, i. e. to the surviving 'they'. In contrast, Sartre's own Principle of Individuation is one's absolute freedom of choice at every moment--one is uniquely defined by one's choices. So, one common definition of 'Existentialism', the principle that 'Existence precedes Essence', is clear in at least Sartre's case--since one chooses one's way of being, that one is precedes what one is. But, Sartre has thus distinguished himself from Heidegger in another important respect. While his Individuation consists in action, Heidegger's moment is one of passive revelation, which he elsewhere characterizes as an "appropriation" of a being by Being, a seeming suppression of Individuality. Meanwhile, the decisive moments of Nietzsche, Kierkergaard, and Jaspers are, like Sartre's, active ones. So, either Heidegger stands as a counter-example to the hypothesis that the locus of Individuality is Action, or he, despite, the common classification, is not an Existentialist.