“Suppose a man and a woman, whom we may call Romeo and Juliet, are at opposite ends of a cocktail lounge, with many mirrors on the walls which permit unobserved observation, and even mutual unobserved observation. Each of them is sipping a martini and studying other people in the mirrors. At some point Romeo notices Juliet. He is moved, somehow, by the softness of her hair and the diffidence with which she sips her martini, and this arouses him sexually. […] Romeo senses Juliet, rather than merely noticing her. At this stage he is aroused by an unaroused object, so he is more in the sexual grip of his body than she of hers.
“Let us suppose, however, that Juliet now senses Romeo in another mirror on the opposite wall, though neither of them yet knows that he is seen by the other (the mirror angles provide three-quarter views). Romeo then begins to notice in Juliet the subtle signs of sexual arousal: heavy-lidded stare, dilating pupils, faint flush, et cetera. This of course renders her much more bodily, and he not only notices but senses this as well. His arousal is nevertheless still solitary. But now, cleverly calculating the line of her stare without actually looking her in the eyes, he realizes that it is directed at him through the mirror on the opposite wall. That is, he notices, and moreover senses, Juliet sensing him. This is definitely a new development, for it gives him a sense of embodiment not only through his own reactions but through the eyes and reactions of another. Moreover, it is separable from the initial sensing of Juliet; for sexual arousal might begin with a person’s sensing that he is sensed and being assailed by the perception of the other person’s desire rather than merely by the perception of the person.
“But there is a further step. Let us suppose that Juliet, who is a little slower than Romeo, now senses that he senses her. This puts Romeo in a position to notice, and be aroused by, her arousal at being sensed by him. He senses that she senses that he senses her. This is still another level of arousal, for he becomes conscious of his sexuality through his awareness of its effect on her and of her awareness that this effect is due to him. […]”
“Another example of such reflexive mutual recognition is to be found in the phenomenon of meaning, which appears to involve an intention to produce a belief or other effect in another by bringing about his recognition of one’s intention to produce that effect. (That result is due to H. P. Grice, whose position I shall not attempt to reproduce in detail.) Sex has a related structure: it involves a desire that one’s partner be aroused by the recognition of one’s desire that he or she be aroused.”
(Nagel, T., 1969, Sexual Perversion. The Journal of Philosophy, 66, 5-17.)