DE Weekly: Monism, Dualism, & Phenomenological Ontology

Like any philosophy, Existentialism boasts a wide array of philosophical thought, owing to the varying worldviews of its most prolific authors; Albert Camus is not the same as Jean-Paul Sartre is not the same as Martin Heidegger is not the same as Søren Kierkegaard. However, there are consistent through points that can be traced in the writings of all of the above.

That being said, we might ask ourselves: is there a common ontology that underpins the whole of existential thought (or at least much of it)?