I recently came across this excerpt from a sermon by Saint John Chrysostom (349-407) on St. Paul's First Letter to the Corinthians. I found his words encouraging in terms of clearly understanding the dynamic between belief and unbelief, the believer and the unbeliever:
We impart the wisdom of God in a mystery (I Cor. 2:7). A mystery does not need to be proved, but simply proclaimed. It would not be a wholly divine mystery if you added to it anything of your own. Besides, the reason it is called a mystery is that we cannot penetrate its depths: what we see is one thing, what we believe is another. In this lies the very nature of our mysteries.
My reactions to them [the mysteries] are therefore different from the reactions of an unbeliever. When I hear that Christ was crucified I am filled with amazement at his love for us, but to the unbeliever this shows weakness. When I hear that Christ became a servant I am astonished at his solicitude for us, but to the unbeliever this is a disgrace. When I hear that Christ died I marvel at his power, since he was not conquered by death, but instead put an end to death. The unbeliever, however, see Christ’s death as a sign of helplessness.
The unbeliever regards the resurrection as pure fiction, but I accept the proven facts and venerate God’s saving plan. In baptism, the unbeliever sees only water, but I perceive not only what meets the eye, but also the purification of the soul by the Holy Spirit. The unbeliever thinks only the body is cleansed, but I believe that the soul also is made pure and holy, and I am reminded of the tomb, the resurrection, our sanctification, justification, redemption, adoption, and inheritance, of the kingdom of heaven and the gift of the Holy Spirit. I judge outward appearances not by what I see but with the eyes of the mind. When the Body of Christ is mentioned the words have one meaning for me, another for the unbeliever.
Just as the letters on a page are meaningless to a child who has not yet learned how to read, so it is with the Christian mystery. Unbelievers are deaf to what they hear, whereas the experience of the Spirit empowers believers to perceive its hidden meaning. Paul made this clear when he said: Our preaching is obscure but only for those on the way to perdition. Something proclaimed everywhere without being understood by those lacking an upright spirit is undoubtedly a mystery. For to the extent that we are able to receive it, it is revealed not by human wisdom but by the Holy Spirit. Rightly, therefore, is the mystery said to be a secret, for even we believers have not been given a completely clear and accurate knowledge of it. As Paul said: Our knowledge and our prophesying are imperfect. We see now as it were a dim reflection in the mirror, but then face to face. This is why he said: We impart the wisdom od God in mystery predestined by God before all ages for our glory.