"It is a basic proposition that God can only be known through God" (John Owen, Biblical Theology, Pg.8).
The monolithic principle of all true theology is that God is the source of all knowledge of himself and of his creation. This is true both immediately when God makes himself known directly to our understanding through regeneration, and mediately when we use methods of science, philosophical reasoning, natural theology, natural revelation, and apologetics as instruments of knowledge for the advancement of our own understanding, persuasion towards belief of unbelievers, and for proofs of various sorts. In all of these things it is God that appropriates knowledge of himself to the heart.
We must be cautious not to stumble at this point. Good theology and apologetics are good only insofar as they accurately reflect the true character and nature of God, as well as our nature as fallen man (It is on this subject that Calvin notes in the opening of the Institutes that "without knowledge of self there is no knowledge of God."), as seen in the light of and in accordance with scripture. There is much thought that does not harmonize with the authority of scripture, and so far as this sort of knowledge is unfaithful to scripture, it is not true knowledge. There is much learning, but never the attainment of divine truth.
It is a foundational and fundamental truth that it is God who awakens us in our knowledge of him, his attributes, and what he requires of man. There is danger in taking too high of a view of man's faculties of reason. No natural man has ever attained to a true knowledge of God by mere intellectual ability, no matter how grand one's science is or how magnanimous one's quality of genius may be.
There are none that have attained to such a high level of insight that they are among a privileged esoteric and even academic priesthood of some unusual sort. Such a notion resembles that of the ancient pagan priesthoods. Arrogance has poisoned the the roots of this tree and though it seems to be alive it is in reality dead.
The origin of Christian knowledge as regards theology is mysterious, but only in that the mystery is revealed to us all by God. No element of a cultic mysticism of any fashion can be found in Christian theology. Owen says, "It is for no such reasons as this that the gospel is ever called a 'mystery,' but rather that the reality of the gospel, as revealed to us men, exceeds all our human reason (1Corinthians 2:7, 14). In order for a man to receive and understand this 'secret and hidden wisdom,' it is first necessary that he himself become a Christian initiate" (John Owen, Biblical Theology Pg. 11). We are convinced by scripture that in the final analysis it is God who gives sight to the blind. It is God that convicts the heart, awakening us to the reality of his divinity, the beauty of his goodness, and the blessings that are in store for those that know him. Unless we are born again we cannot see the kingdom of God.
The matter of a theology secular to scripture falls short and is in the final analysis inert. "This may be scholastic, but it is not founded in faith" (John Owen, Biblical Theology Pg. 12). Good theology, is summarized by Owen in these words: "All of our theology, therefore, flows from that act of divine will by which He wishes to make known this truth to us" (John Owen, Biblical Theology Pg.15). Furthermore he says, "No one can speak or feel worthily about God, or about divine matters, unless he is aided by God, and neither does anyone know God except by His own self-revelation through God the son: nor yet does God wish to be worshipped in any manner but that which He has ordained" (John Owen, Biblical Theology Pg. 16). And again I quote, "True theology is of heavenly origin, declares its own pedigree from above, and must have nothing of man admixed (Matthew 21:25)" (John Owen, Biblical Theology Pg. 16).