Sartre, the well known existentialist of the 20th century, radicalizes human freedom by returning to the ontology of “being”. Human existence lies within a condition of nothingness (no-thing-ness) where things are characterized by what they are not or namely their negation or nihilation (e.g. fragile things lack stable unity). Subjectivity or human experience is divided into pre-reflective and reflective consciousnesses of objects. Pre-reflective consciousness is directed towards the transcendent object without configuring a notion of the “I”; such acts are spontaneous, transparent to the self, and engaged with the phenomenon as a starting point (first-order). Reflective consciousness negates pre-reflective consciousness and so the unity of the negation contains  a duality between some regular agent “I” from memory, and the object. i.e. Consciousness becomes aware of itself. Thus, ego is borne out of reflective consciousness that is imposed upon pre-reflective consciousness. The Other is borne from ego recognizing that is an object of another being’s gaze.

Being can be posited in two way: Things may be in-itself or existing without justification in relation to other things (it is fully determinate). Examples include inert things such as rocks, air,  and bottle. This differs from human beings whose identity is not in relation to things within but always to something else; being for-itself negates being in-itself and can be imagined as a lack of a being. For-itself, through nothingness, is thus able to form attitudes to other beings by seeing what it is not. This desire or project for being gives for-itself a radical freedom to make itself from nothingness. However, the tendency of for-itself to run away from its freedom, to become an in-itself or an absolute (God) is a common way people fall into “bad faith”. This can be applied to the many social roles (waiter, father, lover) that people adopt in their every-day lives; when such roles are no longer functional personas but have been adopted as essences of being (using such roles as excuses for example), than the person is rejecting the task of determining what these roles are not.

The rejection of human nature (existence precedes essence, no essences and priors w.r.t. existence) places agency/freedom is a difficult claim to follow. In Sartre’s day, he rejected the Freudian notions of the unconscious and psychological repression as having an influence on behavior. A priori models such as Jungian archetypes were obviously ignored. Modern advances in genetics and evolutionary biology (our behavior similarities with primates and other hierarchy building animals) would have supplied evidence in the other direction. Here, Sartre’s hedges a bit with his concepts of facticity and transcendence. Facticity is a set of facts viewed from a third person or objectifying stance (e.g. my skin color). Being can be aware of its own facticity but to adopt these facts as determining what I am would once again be in bad faith. The solution is to transcend these facts into what the space of possibilities conditioning upon these facts (e.g. the fact that one is short can be transcended by the behaviors and attitudes on has in light of being short such as humor).

The power the papacy grows and reaches its apex due to removal of older reigimes. Barbarian powers such as Lombards supplanted older emperors and took on different roles w.r.t. culture and faith. In the vicissitudes of state powers exchanged, the Church grew its authorities on faith as it took opportune moments assert its independence. However, authority wasn’t simply the command of the word but also a militaristic one (“Just war”) in the so-called defense of the institution. Ultimately, the great schism between east and western churches was the refusal of the former to submit to such an authority.

The scholastic philosophy that dominated this era (West) was the extension of Aristotle’s metaphysics and logic/dialectic. Western Christianity readily adopted the language and terms set established by their ancestors to define the nature of God. One of the earliest ontological arguments for existence of God was established by Saint Anselm; Russell quotes,
“We define God as the greatest possible object of thought. Now if an object of thought does not exist, another, exactly like it, which does exist, is greater.Therefore the greatest of all objects of thought must exist, since, otherwise, another, still greater,would be possible. Therefore God exists.”
The argument is a play on language where existence is used as a predicate.

Scholasticism culminated with the works of Saint Thomas Aquinas whose beliefs on the nature of God followed the metaphysics of Aristotle. God as actus puras (pure act) is identical with his essence which necessitates his existence; this is analogous to fusing both the Aristolean form and matter in their relation of potentiality and actuality. The existence of God follows from Aristotle’s “unmoved mover” or prime mover / first cause. Last, Thomas asserts that truth is derived from two sources: Natural reason or the logic of man from first principles is the first source. Divine reason or revelation by the grace of God is the second source. Moreover, the two bodies of knowledge derived from these sources can coexist (non-contradictory); this protected the many creeds issued by the Church in a retroactive sense.

Outside of issue of papal authority, the great schism between Eastern and Western churches disagreed on the nature of the trinity of God. From the works of Aquinas, the Western church’s holy trinity (father, son, holy-spirit) belong to the essence of God and are all inter-related but impersonal; each Person is not an treated as an individual per-se but are distinguished via relations with one another. I liken the Father to the universal form of all ideas, the Son as God’s awareness of the forms (self-knowledge) through will/intellect, and the Holy-spirit as an archetypal conscience that is derived from a tension between universals and particulars. The Eastern church disagrees as they center the God head on the Father (personal) as the sole originator of both the Son and the Holy-spirit.

The end of the middle ages is marked by the rejection of universals and the regularization of concepts. William Ockham was a major proponent of this Nominalist movement by asserting that universals didn’t exist but are abstractions via intellect (bottom-up organization); universals are merely words. Ockham’s razor posited that entities should not be multiplied beyond necessity which is to say that solutions or explanations should be parsimonious or as simple as possible. Such a constraint will have a power effect on the enlightenment period where older assumptions are discarded/culled away and the scientific method for acquiring knowledge on nature can advance (in increments).