Abstract
Mystery is a term that permeates and energizes the Catholic tradition. In its strictest terms, it refers to the infinite incomprehensibility of God, but the USCCB speaks also of “the great mystery” of human sexuality. In this essay, only to establish the meanings of mystery as we use the word, we consider, first and briefly, the mystery of God and the oikonomia established by God and, then and more extendedly, the mystery of human sexuality. We offer a meditation on this mystery, leading to a theological understanding of it as a lower-case sacrament of the presence of the incomprehensible God in human history. This analysis leads us to conclude that human sexuality demands ongoing analysis to be better understood physically, psychologically and spiritually in order to be better understood theologically as a lower-case sacrament revelatory of the presence of God.