After the love that unites us to God, conjugal love is the “greatest form of friendship”.122 It is a union possessing all the traits of a good friendship: concern for the good of the other, reciprocity, intimacy, warmth, stability and the resemblance born of a shared life. Marriage joins to all this an indissoluble exclusivity expressed in the stable commitment to share and shape together the whole of life. Let us be honest and acknowledge the signs that this is the case. Lovers do not see their relationship as merely temporary. Those who marry do not expect their excitement to fade. Those who witness the celebration of a loving union, however fragile, trust that it will pass the test of time. Children not only want their parents to love one another, but also to be faithful and remain together. These and similar signs show that it is in the very nature of conjugal love to be definitive. The lasting union expressed by the marriage vows is more than a formality or a traditional formula; it is rooted in the natural inclinations of the human person. For believers, it is also a covenant before God that calls for fidelity: “The Lord was witness to the covenant between you and the wife of your youth, to whom you have been faithless, though she is your companion and your wife by covenant… Let none be faithless to the wife of his youth. For I hate divorce, says the Lord” (Mal 2:14-16).
A love that is weak or infirm, incapable of accepting marriage as a challenge to be taken up and fought for, reborn, renewed and reinvented until death, cannot sustain a great commitment. It will succumb to the culture of the ephemeral that prevents a constant process of growth. Yet “promising love for ever is possible when we perceive a plan bigger than our own ideas and undertakings, a plan which sustains us and enables us to surrender our future entirely to the one we love”.123 If this love is to overcome all trials and remain faithful in the face of everything, it needs the gift of grace to strengthen and elevate it. In the words of Saint Robert Bellarmine, “the fact that one man unites with one woman in an indissoluble bond, and that they remain inseparable despite every kind of difficulty, even when there is no longer hope for children, can only be the sign of a great mystery”.124
Marriage is likewise a friendship marked by passion, but a passion always directed to an ever more stable and intense union. This is because “marriage was not instituted solely for the procreation of children” but also that mutual love “might be properly expressed, that it should grow and mature”.125 This unique friendship between a man and a woman acquires an all-encompassing character only within the conjugal union. Precisely as all-encompassing, this union is also exclusive, faithful and open to new life. It shares everything in constant mutual respect. The Second Vatican Council echoed this by stating that “such a love, bringing together the human and the divine, leads the partners to a free and mutual self-giving, experienced in tenderness and action, and permeating their entire lives”.126