In her introduction to Finite and Eternal Being: An Attempt at an Assent to the Meaning of Being Edith Stein concludes by indicating the limits of human knowledge regarding truth, as achieved by theology or philosophy. For unlimited access to the truth one needs God's direct personal guidance: living faith.
...The realization of the ideal (of the Medieval Summae to provide a monumental and comprehensive presentation of...total knowledge)--in the sense of a total comprehension of reality in its unity and plenitude--transcends the capacity of any and all human Wissenschaft. Even finite reality can never be exhaustively understood by means of conceptual knowledge, and much less the infinite reality of God. Thus pure philosophy as a Wissenschaft of beings and of being, in the light of the ultimate reasons and causes (and staying within the confines of natural reason), remains even in the greatest conceivable perfection essentially fragmentary. But it is candid in respect to theology and may thus be complemented by it. Nevertheless, even theology is not a closed nor an absolutely conclusive structural whole. It evolves historically in a progressive appropriation and penetration of the original contents of revealed truth.
Furthermore, it must be emphasized that the contents of revelation do not comprise the infinite plenitude of divine truth. God reveals himself to the human mind in a measure and manner commensurate with his wisdom. His sovereign will may see fit to enlarge this measure and to reveal the divine mysteries in a way commensurate with the modes of human thinking: with discursive reasoning, conceptual knowledge, and critical judgment. Or he may raise human beings above their natural ways of thinking to a totally different level of knowledge, making them partakers of that divine vision which embraces everything with one single and simple glance.
The perfect fulfillment of everything at which philosophy--as a striving toward wisdom--aims, is the divine wisdom itself, the simple visio with which God embraces himself and all his creation. The highest perfection to which a created spirit may attain--but, to be sure, not without divine aid--is the beatific vision. This is the divine gift of union with God by which the created spirit partakes of divine knowledge in sharing divine life. The mystical vision or mystical union represents the closest approximation to this highest goal that is attainable in this earthly life. A preliminary stage, however, for which this highest favor is not required, is a true and living faith.
Theological terminology designates as faith not only the virtue (fides, qua creditur) but also the contents of faith, namely, the revealed truth (fides quae creditur) and, moreover, the vital actualization of the virtue of faith (credere, actual faith) or the act of faith. And it is this living and actual faith with which we are here concerned.
Several elements are implicit in the act of faith: By accepting the truths of faith on the authority of God, we hold them to be true and thereby give credence to God (credere Deo). But we cannot give credence to God unless we believe in God (credere Deum), that is, unless we believe that God is and the he is God: We use the name God to designate the supreme and absolutely truthful being.
To accept the truths of faith means thus to accept God, for God is the real object of faith, and to him all the truths of faith are related. But to accept God also means to turn to him in our faith or to believe in God as the end of our faith (credere in Deum), that is, to strive toward God. Faith is thus a taking hold of God. This kind of seizure, however, presupposes a being seized. In other words, we cannot believe without divine grace. And grace means participation in divine life. Once we open ourselves to grace and accept the gift of faith, we have "within us the beginning of eternal life."
We accept faith on the testimony of God himself and thereby gain a certain knowledge without, however, obtaining a thorough comprehension. In other words, we cannot accept the truths of faith as evident in themselves as we do in the case of the necessary truths of reason or of the data of sense perception; nor can we deduce them logically from certain self-evident truths. This is one reason why faith is called a "dark light." Moreover, faith as a credere Deum and a credere in Deum always aspires beyond all revealed truth, that is, beyond all truth which God has confined in concepts and judgments, in words and sentences, in order to make it commensurate with the human mode of cognition. Faith asks of God more than individually separated truths: It desires God himself, all of him, who is the truth, and it seizes him in darkness and blindness ("although it is night").
This night denotes the profound darkness of faith as compared with the eternal light to which it aspires. And our holy father, St. John of the Cross, refers to this dual darkness of faith when he writes, "In the course of the progress of the understanding, faith becomes stronger, and thus this progress brings on increasing darkness, since faith is darkness for the human reason." But it is an advancing, nevertheless, a going beyond all conceptually intelligible particularized knowledge unto the simple comprehension of the one truth. Faith therefore is closer to divine wisdom than any philosophical or even theological knowledge and science [Wissenschaft]. But because it is difficult to go forward in the dark, every ray of light that pierces our night gives us a glimpse of the future brightness and is therefore an invaluable aid in keeping us from going astray. And thus even the feeble light of natural reason may render good service.
A Christian philosophy will regard it as its nobles task to prepare the way for supernatural faith. This is the precise reason why St. Thomas was so deeply concerned with the problem of how to build a pure philosophy on the basis of natural reason. He knew well that this was the only way of finding some common ground with unbelieving thinkers. If the latter are willing to join us at least part of the way, they may perhaps subsequently allow themselves to be guided farther than they originally intended to go. From the point of view of Christian philosophy, there should then be no misgivings about a common effort. Adhering to the principle, "Examine everything, and retain the best," Christian philosophy is willing to learn from the Greeks and from the moderns and to appropriate for itself whatever can meet the test of its own standards of measurement. On the other hand, it can well afford to display generously what it itself has to offer and then leave to others the task of examination and selection.
Unbelievers have no good reason to distrust the findings of Christian philosophy on the grounds that it uses as a standard of measurement not only the ultimate truths of reason but also the truths of faith. No one prevents them from applying the criterion of reason in full stringency and from rejecting everything that does not measure up to it. They may also freely decide whether they want to go further and take account of those findings which have been gained with the aid of revelation. In this case they will accept the truths of faith not as "theses" (as do believers) but only as "hypotheses." But as to whether or not the conclusions at which both arrive are in accord with the truths of reason, there prevails again a standard of measurement which both sides have in common. Unbelieving thinkers may then calmly consider whether or not they find themselves able to make their own the synthesis which results for Christian philosophers from the two sources of reason and revelation. And unbelievers must judge for themselves whether by accepting this additional knowledge they may perhaps gain a deeper and more comprehensive understanding of that which is. They will at any rate not shrink back from such an attempt if they are really as unbiased as, according to their own conviction, genuine philosophers ought to be.