The open-ended presence of the past as retaining the vital spark of each lived moment is what Sartre means by 'facticity'. It is not the object of an intentionality but a property of the intentionality itself, and at the same time it is positive content which accumulates. How is this not an immanence, an unaccountable objectivity in the heart of pure subjectivity? It belongs to what you would call soul if that term retained any explanatory power. The soul can be cleared of, or washed clean of, whatever in memory is opaque without actually losing all memory, it becomes both particular and universal, sublimed. Everything that was merely contingent becomes necessary, is taken under eternity. Contingency itself falls under eternity. This is mysterious but it answers to the sense that whatever is original is purely particular, at the same time as in being original it is necessary and hence universal. You cannot get there by way of abstraction, you must take the opposite route, into the thing itself.