Verified by 
"Sex without love is an empty experience, but as empty experiences go, it's one of the best." —Woody Allen
"I have never liked sex. I do not think I ever will. It seems just the opposite of love." —Marilyn Monroe
"I know nothing about sex, because I was always married." —Zsa Zsa Gabor
What is the relationship between romantic love and sexual desire? Is it true that "love ain't nothing but sex misspelled," as Harlan Ellison claimed, or are they two separate emotions? A plausible answer is that the two are not identical, but have significant links. What are these links, and are they subject to gender differences?
Is sex central to love?
Like love, sexual desire is also an emotion and not a mere biological drive, like hunger and thirst. Sexual desire is typically part of romantic love. The complex experience of romantic love involves two basic evaluative patterns referring to (a) attractiveness—that is, an attraction to external appearance, and (b) praiseworthiness—that is, a positive appraisal of personal characteristics.
Although sexual desire involves both types of evaluations, the emphasis is upon attractiveness. Accordingly, the mental capacities involved in sexual desire are more primitive than those involved in romantic love.
Sexual desire is focused on short-term details of a few external parts of the person's body that can be instantly revealed by sense perception. In love, more long-term, comprehensive evaluations are involved. In love, we see the forest, whereas, in sexual desire, we focus upon one or several trees. The limited nature of sexual desire is indicated in the notion of a "one-night stand" (Förster et al., 2009).
The connection between sexual desire and romantic love has significant evolutionary advantages for mating and having more offspring. However, this connection also raises difficulties.
Romantic love has often been considered to be one of the most meaningful and sublime human expressions. At the same time, sex has often been criticized for involving vulgar, disgusting, and humiliating activities and for degrading or turning the partner into a commodity. As one woman said, "I've always hated knowing that men wanted to have sex with me without any emotional involvement. I think I trigger sexual desire in almost every man, and it has nothing at all to do with love."
It is therefore surprising that some people, many of whom are religious or conservative, who have voiced such fierce criticism of sex also consider sexual exclusivity as the hallmark of romantic love and its violation as the greatest desecration of the romantic bond.
If sex is not the essence of romantic love, why do we attribute such a great weight to sexual exclusivity in romantic relationships? It can be argued that from a psychological perspective, the gravest violation of the romantic bond is a profound emotional involvement rather than a superficial sexual activity with another person.
One reason for this may be that sexual activities often entail such profound involvement. This, however, indicates that the essence of love is not the sexual activity itself, but is rather the emotional involvement, which sometimes, but not always, is associated with it. Sex may occur without love, but romantic love at its best usually includes sex.
Recent scientific evidence indicates the affinity between sexual desire and love: Despite their differences, they recruit a remarkable common set of brain areas. They activate specific but related areas in the brain (Cacioppo et al., 2012).
Sex and marriage
Not long ago, the sexual realm was normatively limited (mainly for women) to marriage, whereas most sectors of modern society now consider it an acceptable part of casual relationships before and after marriage. The only stronghold that the sexual revolution has failed to destroy is the prohibition against married people having sex with people other than their spouses. Married people seem to be normatively allowed to do almost anything with other people—except engage in sexual activity.
Will married people be allowed to join the party sometime in the future and satisfy their sexual needs outside of their committed framework? Do the boundaries of marriage reflect profound moral or psychological boundaries, or are they rather, as George Bernard Shaw said, "the Trade Unionism of the married"? Not unlike other trade unions, that of the married couple attempts to keep its existence by postulating rigid boundaries. Do such boundaries make people happy at the end of the day?
Returning again to Shaw's ironic formulation, "If the prisoner is happy, why lock him in? If he is not, why pretend that he is?" Although there is no indication that the course of the sexual revolution has ended, the answers to the questions above are not clear, as sexual relationships are deeply associated with the very core of romantic relationships. It seems certain, however, that no simple answer can be appropriate to everyone in all circumstances (In the Name of Love).
Caring and love
Caring, which promotes the partner's flourishing, has more significance in romantic love than does exclusive sex, which prevents the partner from engaging in certain activities. Indeed, in the Aristotelian view, the essence of love is to act for the good of someone else for their sake alone. Caring is such an activity; sex is seldom so.
Indeed, in defining love, Aristotle does not mention the pleasure and pain associated with it; this may indicate that he views these emotions as ancillaries to love. Given that a personal caring attitude is crucial for profound romantic relationships, sex is not the best choice for defining the essence of romantic love, even though caring and sex can complement each other.
It is easier to detect violations of crossing boundaries, such as the prohibition of extramarital sex, than violations of promoting principles, such as the enhancement of care. But this is not a profound reason for postulating sex as the essence of love. Caring is more significant in genuine romantic relationships than exclusive sex is. There is no love without caring, but there may be love devoid of sex. Since caring does not entail strict exclusivity in the sense attributed to sex, such exclusivity may not be so essential to romantic love.
Sex as an intrinsically or an extrinsically valuable activity
The dispute about the value of sex can be clarified by considering the Aristotelian distinction between an extrinsically valuable activity, which is a means to achieving an external goal, and an intrinsically valuable activity whose value stems from the activity itself, not from its results (see here).
When sex is combined with profound romantic love, it is part of the ongoing intrinsically valuable experience of love. Love and sex here are essential for the agent's flourishing.
Sex can also exist without love, and in this case, it can be either an extrinsically valuable activity or a superficial intrinsically valuable activity. In the case of commercial sex and other purposive sexual relationships, sex is an extrinsically valuable activity in which the other is used as a means to satisfy one's sexual desire or to gain wealth, status, or attention.
Sex without love can also have an intrinsic value, but this is typically more superficial—similar to the value of watching television. Such superficial pleasure is an immediately rewarding, relatively short-lived experience requiring few or no profound human capacities. This pleasure does not sustain the individual's flourishing in the long term. This is the difference between a fleeting pleasure and a lasting treasure.
The combination of sex and love can be the greatest expression of human happiness. However, it is not a necessity or the essence of love. There are women who have not experienced an orgasm for many years, even though they love their partner. Some men experience intense sexual pleasure by having casual sex with prostitutes or other women and not with the woman they love and respect. Love can also limit sexual pleasure and not merely intensify it.
The superficial and limited value of sexual activities without love is expressed in the morning-after effect. In some cases, superficial intrinsically valuable activities may even have a negative functional value, since we may pursue them instead of engaging in more beneficial activities. However, sometimes sex without love can generate profound love in which sex is part of the ongoing intrinsically value experience of love.
Gender differences
The issue of whether sex is or is not an essential part of romantic love depends on various personal and contextual circumstances, such as gender, age, culture, and the intensity of love. Here, I will discuss the gender issue.
Many people believe that there is a link between romantic love and sexual desire. In one study, conducted by Dorothy Tennov, over 90 percent of the subjects rejected the statement: "The best thing about love is sex." Similarly, 53 percent of the females and 79 percent of the males agreed with the statement: "I have been sexually attracted without feeling the slightest trace of love"; and 61 percent of the females and 35 percent of the males agreed with the statement: "I have been in love without feeling any need for sex."
Indeed, men tend to separate sex and love, whereas women tend to believe that love and sex go together. Thus, erotic pictures generate more arousal in men than in women, whereas pictures of romantic couples generate more arousal in women than in men. Similarly, women's extramarital sexual involvements are more likely to be love-oriented, and those of men tend to be pleasure-oriented.
Accordingly, men are more likely to engage in extramarital sex with little or no emotional involvement, whereas women are more likely to engage in extramarital emotional involvement without sexual intercourse. The majority of people, especially women, enjoy sex best when they are in love with their partner. Thus, most people think that love and sex can be separated but would prefer to have them combined.
When examining romantic regrets, Roese and his colleagues (2006) argue that "Men are vastly more likely than women to regret not trying harder to have sex or to regret missing an opportunity for sex." Since casual sex tends to confer more benefits and fewer costs on men than on women, men express greater willingness for casual sex. Women tend more than men to focus on keeping matters of romance from deteriorating in their own relationships.
It appears that sexual desire in men is often a kind of limited and specific hunger; in women, it is more often an aperitif which should be complemented with a full course of the meal of love.
Conclusion
No precise borderline between romantic love and sexual desire exists. The latter usually is an essential component of the former. Hence, elements that are typical of the one are often found in the other.
The close relation between romantic love and sexual desire indicates that we cannot be as unromantic about sex as we are about eating, but it does not rule out cases in which sexual desire has nothing to do with romantic love. Society may need an orderly correlation between love and sex, but nature encourages disorderly mating involving both love and sex, and it allows space for various ways in which they can relate.
The above considerations can be encapsulated in the following statement that a lover might express: "Darling, I desire you so much sexually, but do I have to love you as much?"
