According to Catholic moral theologians, is it more conducive to the unbaptized's possible salvation to marry (other unbaptized) or remain single?
Better to marry than to burn with passion, as Saint Paul wrote. Marriage, even outside of proper sacramental matrimony, are still real natural marriages. Chastity is demanded of both the married and unmarried; in the unmarried, chastity is expressed through celibacy, and in the married, through fidelity. A faithful marriage between two perfidis Jews may be less prone to moral corruption than the solitude of an unmarried yet unchaste Jew of a similar background and circumstance.
The unbaptized have Original Sin and thus lack sanctifying grace. This makes it impossible for them to conquer concupiscence, the "Insubordination of man's desires to the dictates of reason".
Married Christians have two ways to remedy concupiscence:
- the marriage act
by hindering the shameful act, which is done by the very nature of the act because concupiscence, being satisfied by the conjugal act, [one] does not incline so much to other wickedness. For this reason the Apostle says (1 Cor. 7:9): "It is better to marry than to burn."
—St. Thomas Aquinas, Summa Theologica suppl. q. 42 a. 3 ad 4
The unmarried unbaptized have neither of these helps, but the married unbaptized have help #2; therefore, it is better for the unbaptized to marry.