First, to define Eros—Eros is love between the sexes, which includes sexual attraction but is not merely sex. It is what people mean when they talk about “being in love” with someone. Sex itself, which Lewis calls Venus, is only a part of it, and not even the greatest part. Venus can exist outside of Eros, and Eros can exist, and often does exist, without any thought of sex or sexual interaction.
Furthermore, the presence or absence of Eros doesn’t make an action morally right or wrong. For example, in ages past many people married and had children who were not in love, but simply obeying the wishes of their parents and fulfilling their duty towards society and each other, and, as Lewis says, “they did right.” Just because Eros was not present doesn’t make the sexual act wrong. In the same way, a man who commits adultery because he is in love with a woman who is another man’s wife does wrong even though his actions grow out of Eros. This ties back to “We Have No Right to Happiness”—even though Eros speaks with an almost divine voice and makes lofty promises and terrible threats, it cannot justify otherwise immoral acts—dishonesty, faithlessness, the breaking of promises and the betrayal of loved ones.At its beginning, Eros is rarely concerned with sex. It begins most often with a preoccupation with another person, all his or her likes and dislikes, mannerisms and habits, way of speaking and moving and laughing. Sex doesn’t even enter into the lover’s mind. To a man just starting to fall in love, the fact that his beloved is a woman, and even a sexually attractive woman, is beside the point. He is only concerned with the fact that she is herself. Eventually, sexual desire becomes a part of Eros, but it does so as “[an institution] of a conquered country.” Eros “reorganizes” sex, and so sex inside of Eros is quite different from sex outside of it. Lewis points out that many medieval moralists and theologians tended to think that the more Eros detached itself from Venus, the purer it would be; sex was a pollutant, a temptation to sensual gratification and lust. As most of these men were celibates, however, Lewis argues that they could not have known how Eros transforms sexual desire, “how, far from aggravating, he [Eros] reduces the nagging and addictive character of mere appetite…[making] abstinence easier.”