Christianity

The Christian understanding is that love comes from God. The love of man and woman— eros in Greek—and the unselfish love of others (agape), are often contrasted as "ascending" and "descending" love, respectively, but are ultimately the same thing.

There are several Greek words for "love" that are regularly referred to in Christian circles.

• Agape: In the New Testament, agapē is charitable, selfless, altruistic, and unconditional. It is parental love, seen as creating goodness in the world; it is the way God is seen to love humanity, and it is seen as the kind of love that Christians aspire to have for one another.
• Phileo: Also used in the New Testament, phileo is a human response to something that is found to be delightful. Also known as "brotherly love."
• Two other words for love in the Greek language, eros (sexual love) and storge (child-to-parent love), were never used in the New Testament.

Christians believe that to Love God with all your heart, mind, and strength and Love your neighbor as yourself are the two most important things in life (the greatest commandment of the Jewish Torah, according to Jesus; cf. Gospel of Mark chapter 12, verses 28–34). Saint Augustine summarized this when he wrote " Love God, and do as thou wilt. "

Christian theologians see God as the source of love, which is mirrored in humans and their own loving relationships. Influential Christian theologian C.S. Lewis wrote a book called The Four Loves. Benedict XVI wrote his first encyclical on "God is love". He said that a human being, created in the image of God, who is love, is able to practice love; to give himself to God and others (agape) and by receiving and experiencing God's love in contemplation (eros). This life of love, according to him, is the life of the saints such as Teresa of Calcutta and the Blessed Virgin Mary and is the direction Christians take when they believe that God loves them.

In Christianity the practical definition of love is best summarised by St. Thomas Aquinas, who defined love as "to will the good of another," or to desire for another to succeed. This is the explanation of the Christian need to love others, including their enemies. As Thomas Aquinas explains, Christian love is motivated by the need to see others succeed in life, to be good people.