1. The direct answer is: Partly but not completely. Love of God and love of neighbor express the moral implications of Christian love to the extent that norms expressed in the Old Testament law remain true for Christians.2 However, while these two commands sum up the moral implications of Jewish faith, Christian love not only summarizes but fulfills the law and the prophets. Love of God and love of neighbor do not fully express the moral implications of Christian love.
2. The synoptic Gospels contain accounts of Jesus’ specific teaching on the commands to love God and neighbor. Jesus is variously reported to have been asked by a hostile Pharisee which is the great commandment (see Mt 22.34–40), by a friendly scribe which is the first commandment (see Mk 12.28–34), and by a minimalist lawyer what one must do to gain eternal life (see Lk 10.25–29). In reply, he cites the familiar injunction to love God (see Dt 6.5) and adds to it the command to love one’s neighbor, which also belongs to the Old Testament (see Lv 19.18).3
3. All the accounts make it clear that love of God and love of neighbor are so closely linked by Jesus that they can be taken as a single, complex norm. Insofar as they express the foundation for the whole law and prophets, they must be considered a formulation in religious terms of the first principle of morality (see S.t., 1–2, q. 99, a. 1, ad 2; q. 100, a. 3, ad 1; 2–2, q. 44, aa. 1, 3).
In both the Old Testament and the New, the claims which love makes upon human persons always presuppose God’s merciful and faithful love for sinful men and women. God loves first; he offers the covenant. This fact creates a new situation for human moral life. The new situation is what transforms the basic requirement that one’s will be toward integral human fulfillment into the commandments of love of God and neighbor. For all human hope of fulfillment depends upon God’s mercy and faithfulness, and the human contribution to this fulfillment is to do good—or, at least, to avoid harm—to one’s human fellows, particularly to members of the covenant community.
In the context of the covenant, faith is acceptance of and commitment to the covenant relationship, hope is confidence that God will carry out his part of the covenant faithfully and fulfill all his promises, and love is the readiness to carry out one’s own part in the covenant. Thus, the command to love is the demand to keep the commandments, to do the will of God. There is no special and separate act of loving God; love is a disposition to the goods shared in the covenant community with God. It includes both his honor (by exclusive worship of him) and the well-being of the community (which is ensured partly by human effort and respect for the goods protected by the commandments regarding one’s neighbor, but mainly by divine care and intervention).
4. Under the impetus of the belief that Yahweh is the God of all creation and so of all nations and peoples, love of neighbor tended to expand in the Old Testament beyond any set boundaries. By the parable of the Good Samaritan, appended to one Gospel’s treatment of the first commandment (see Lk 10.30–37), Jesus teaches that the neighbor is whoever is prepared to do good to others and implies that the commandment of love enjoins unrestricted concern for human fulfillment. In sum, the commandments to love God and love neighbor remain within the framework of the old covenant, while the parable of the Good Samaritan hints at a fulfillment of the law and the prophets which goes beyond them.
Some proponents of the so-called new morality have opposed the love commandments to specific moral norms and invoked the text of the Gospels as a premise in their argument for proportionalism. However, in the context of the law and the gospel, the commandments of love by no means suggest that one might rightly override specific moral norms to pursue what intuitive sympathies might lead one to identify as a greater good or lesser evil in particular cases. Indeed, virtually the same question about the way to heaven which introduces the commandment of love in one context (see Lk 10.25) in another context (see Mt 19.16) introduces the discussion of voluntary poverty which presupposes the keeping of the specific commandments, of which the command to love one’s neighbor is given as a sort of summary (see Mt 19.18).
2. The fact of continuity makes it very worthwhile to understand the idea of commandment in the Old Testament. See Matthew J. O’Connell, S.J., “The Concept of Commandment in the Old Testament,” Theological Studies, 21 (1960), 351–403. Much recent critical work on the life of Jesus gives the love commands a more ultimate place in his ethic than I do. See Gustaf Aulén, Jesus in Contemporary Historical Research, trans. Ingalil H. Hjelm (Philadelphia: Fortress Press, 1976), 17–54. However, the account provided of the moral significance of the love commands differs little from the content chapter twenty-six will derive from the Beatitudes: that one must seek and expect everything from God, utterly submit to his will, give up everything else for his kingdom, and be wholehearted about it; that one must will and do good to everyone, even enemies.
3. See the generally helpful exegetical study: Pheme Perkins, Love Commands in the New Testament (New York: Paulist Press, 1982), esp. 10–25 and 104–21. Theological interpretations in this volume, especially those drawn from recent work of Schillebeeckx, must be treated critically.