When Christianity first appeared, ancient Greek civilization was already present there. Thus, Christianity was challenged in various ways from the very beginning, and it was justified in taking the path of self-explanation. It was faith seeking understanding, and this understanding could only be achieved through ancient Greek philosophy.
And, this integration requires that Christianity return from a symbolic culture to the fact of first cause, without which integration is not possible. This puts pressure on faith; if faith is comprehensible, then what is the point of its existence?
Thus, the original Christian theologians declared that reason serves faith.
The early Christian theologians were well versed in ancient Greek philosophy, and it is not at all surprising that they were the ones who achieved the fusion of faith and reason. Justin the Martyr began by stating, "True philosophy is true religion, and true religion is true philosophy." This judgment is undoubtedly correct.
But how is this fusion possible? These Christian theologians then introduced Heraclitus' Logos. The Gospel of John begins with the words, "In the beginning was the Word, and the Word was with God, and the Word was God." This Word is the Logos. There is a certain difference between God and the Logos, if we want to look into it. For God is the first cause, while the Logos is used to identify entities. However, since they are associated with the same chaotic fact, then this expression still has validity.
The expression "the Word is God", which is the fusion of reason and faith, is very clear. But what is the Logos again? This actually required the ancient Greek philosophers to give universal knowledge, but of course they failed to achieve this, and the Logos remained an implicit knowledge, which could only be understood by a very small number of people.
Obviously, this integration is not ideal and risks putting faith in danger of being assimilated into reason. At the same time, it does not reflect the qualities of faith itself. Thus, another construct emerged that better reflects the qualities of faith, namely the doctrine of the Trinity.
The Trinity is the trinity of the Father, the Son, and the Holy Spirit. In this structure, the Father is the first cause, the Son is the entity, and the Holy Spirit is the absolute entity, which embodies both the qualities of faith and the spirit of reason, and is thus a perfect fusion of faith and reason.
In the Trinity, all are God from the point of view of faith, and the relationship between God and man is revealed from the point of view of reason: man became incarnate as an entity, the Son, because of the First Cause, the Father. This means that man needs to realize his physical existence in faith, and Jesus Christ is an example of the physical existence of man.
It is evident that in the fusion of faith and reason, it is actually reason, not faith, that is to be moved toward. This is not to the detriment of faith, except that reason itself remains in the mist.
Since faith and reason have merged in the structure of the Trinity, why did Christianity later introduce Neoplatonism and Aristotelianism? Because the spirit of reason in this Trinitarian structure, like the Logos, remains in a state of invisibility, and then it cannot be universally understood.
And since universal understanding is a real desire, these ideas are introduced into the interpretation of faith because of their "intelligibility. Neoplatonism gives a specific model of interpretation, in which the highest level is the "oneness", and the "oneness" overflows into the nus, and the nus overflows into the soul, and below the soul is the sensible world. The soul can turn to the Oneness through the Nuss, or it can turn to the sensible world, but the mission of man is to return to the Oneness. This model of interpretation was accepted by Augustine, but he transformed it.
By saying "you know that you are thinking," Augustine discovered the inner immediacy of man, and this discovery led to his existence as an entity. Augustine said, "The truth is within man, for the human mind does not know anything except what is presented to the mind." He did discover the truth and combined his inner world with the Neoplatonic mode of interpretation, which amounts to a direct confrontation with the "too-one", which is God.
Augustine actually gives reality to this mode of interpretation, for Neoplatonism itself is only symbolic. When intrinsic immediacy enriches this mode of interpretation, the idea of hierarchy in it is unnecessary, and Augustine dissolves it.
But the question is, how is this intrinsic directness itself possible? When intrinsic immediacy cannot be given, then this transformed Neoplatonism must not be truly understood either.
Thus, understanding remains limited, but Augustinianism is significant because it points out that the truth is in the inner immediacy of man. Thus, a new faith emerged, a faith that no longer believed in a symbolic God, but that man had faith in his own inner immediacy.
This new faith is so secret that it and reason are actually in the same fact. As long as reason can confirm the first cause, faith can confirm it in its inner immediacy, and then the fusion of reason and faith is a reality.
But reason is not yet able to achieve this, and it is indeed impossible for faith to confirm the first cause in inner immediacy, and thus they remain in faith.
That is, in this inner immediacy, reason and faith still cannot be truly fused.
This delicate balance between faith and reason lasted for centuries until Aquinas introduced Aristotelianism. Aristotelianism is essentially a reformed Platonism, and there is a rift between Plato's idea and being, which leads to the idea not having a reality. Aristotelianism, then, does not have a reality either, that is, the doctrine itself has nothing to do with reason.
This means that it is inappropriate to try to fuse faith and reason by introducing Aristotelianism, and the reality shows this, because this new fusion eventually leads to an irreconcilability between faith and so-called reason.
The Augustinians opposed the Aristotelians represented by Aquinas, though not because they were able to detect the irrationality of Aristotelianism, but because they discovered the fact that this new interpretation departed from intrinsic immediacy.
One thing that is surprising is that the people of this age no longer seem capable of understanding what is truly rational in the way that the original theologians did.
It was the fact that Aristotelianism was not truly rational that made it questionable from the very beginning. This questioning was further expressed in the debate between nominalism and realism.
Nominalism rejects the notion of the coeval as real, which originates from Plato's conceptualism. This also implies a rejection of Platonism. Nominalism is intended to point out that God can only be used for belief, and that it is impossible for reason to know Him.
However, this nominalist thought apparently did not realize what real reason is. Thus, a worst reality emerges, where the original integration between faith and reason is disregarded, because it is no longer understood.
The nominalists could not understand it because they could not actually understand faith itself either. The final breakdown of this fusion meant the arrival of modernity.