I have long been wishing, O true-born and dearly beloved children of the Church, to discourse to you concerning these spiritual, and heavenly Mysteries; but since I well knew that seeing is far more persuasive than hearing, I waited for the present season; that finding you more open to the influence of my words from your present experience, I might take and lead you to the brighter and more fragrant meadow of the Paradise before us.
For ye are now capable of receiving the more Divine Mysteries, after having been found worthy of Divine and life-giving Baptism. Since therefore it remains to set before you a table of the more perfect instructions, let us now teach you these things exactly, that ye may know the effect wrought upon you on that evening of your Baptism.
Cyril's opening explains the ancient practice of the disciplina arcani — the discipline of the secret — whereby the full explanation of the sacraments was withheld from catechumens and given only after they had received Baptism. The reasons are pastoral and theological at once. Pastorally: the unbaptised had not yet experienced the realities being described, and description without experience breeds superficial knowledge. Theologically: the sacraments are mysteries in the strict sense — actions of God that exceed human comprehension and are entered into before they are fully understood. The implication for apologetics is important. Cyril is not speculating about what the Eucharist or Baptism might mean. He is explaining, to people who have just received them, what they have already experienced. The descriptions that follow are not theological proposals but explanations of completed acts. When Cyril says the bread is the Body of Christ, he is telling the newly baptised what they already received at the altar. The clarity of this context destroys any interpretation of his language as merely symbolic.