“I BESEECH you therefore, brethren, by the mercy of God, that you present your bodies a living sacrifice, holy, pleasing unto God, your reasonable service.” (Rom. 12:1)
In this passage, Saint Paul employs specifically liturgical language. For “sacrifice,” the Latin is hostiam and the Greek, θυσία — both words connoting sacrificial oblations made to God. For “your reasonable service,” the Latin is rationabile obsequium vestrum, and the Greek, λογικὴν λατρείαν ὑμῶν. Both obsequium and, still more, λατρείαν, have liturgical implications, the former being found in the “Pláceat” prayer of the traditional Latin Mass (just before the final blessing), and the latter being the Greek word we render “adoration” in English, signifying the sacred worship that is due to God alone (see here and here).
Monsignor Ronald Knox’s translation is helpful to convey the fuller meaning: “And now, brethren, I appeal to you by God’s mercies to offer up your bodies as a living sacrifice, consecrated to God and worthy of his acceptance; this is the worship due from you as rational creatures.”
As a “living sacrifice,” the bodies of all Christians are to be offered to God not to be slain but to be immolated by all the mortifications required to live a virtuous Christian life. When, by a religious consecration, we add the counsels of poverty, chastity, and obedience to our Baptismal life, then we have additional mortifications that flow from the vows, each one of which is intended to remove obstacles to the full flowering of Christian virtue.
Living as we do in time when the ongoing sexual revolution that has reached a stage we might call preternaturally perverse, the mortifications most closely associated with chastity are the ones the world most notices.
Because the human body has life — specifically, sentient life — it has appetites. Certain of these appetites are there to sustain life, either in the individual organism itself (food), or in the species (reproduction). In the rational animal, these appetites must be regulated in accordance with the Divine Law and directed by the virtue of temperance. But temperance itself is not enough. Love is needed, specifically that love we know as charity, which orders all our loves to the love of God. The lovers of God have appetites, too, but they are subject to the one supreme appetite — the hunger and thirst after justice. This appetite, which God promises to satiate, moves us to sustain the divine life in us, that is, the spiritual life or the life of grace.
The Catholic religious chooses the life of vowed, celibate chastity. He chooses to be a “eunuch for the kingdom of heaven” (Matt. 19:12). Thereby, he intends to offer his body as a “living sacrifice.” Precisely because his body is living and not dead, it has in it all those natural impulses God has built into us to sustain life — both for itself and for the species. For a higher principle, a higher life, the consecrated celibate offers up the non-fulfillment of the powers of reproduction, along with the comforts of hearth and home that accompany their lawful use, for the kingdom of Heaven, that is, for the higher purpose of supernatural life. That life must be fruitful — fruitful unto good works, fruitful unto virtue, fruitful unto the glory of God.
Seen in this light, the religious aims, not at the fecundity that God commanded to our parents in the Garden of Eden (“Increase and multiply, and fill the earth…” [Gen. 1:28]), but at the higher fecundity spoken of by Jesus Christ: “Abide in me, and I in you. As the branch cannot bear fruit of itself, unless it abide in the vine, so neither can you, unless you abide in me. I am the vine: you the branches: he that abideth in me, and I in him, the same beareth much fruit: for without me you can do nothing” (John 15:4-5).
The way for our lives to be fruitful is the way of piety, which is defined as the pursuit of God’s glory first and my happiness second by knowing, loving, and seeking God in all things, allowing nothing to remain an obstacle to that pursuit. In this is unity, strength, stability, peace, and fecundity. In this is true life. Opposed to it is seeking our own selfish satisfaction, which causes disunity, division, dissipation, and, ultimately, death.