by Alian de Botton
Involuntary physiological reactions such as the wetness of a vagina and the stiffness of a penis are emotionally so satisfying (which means, simultaneously, so erotic) because they signal a kind of approval that lies utterly beyond rational manipulation. Erections and lubrication simply cannot be effected by willpower and are therefore particularly true and honest indices of interest. In a world in which fake enthusiasms are rife, in which it is often hard to tell whether people really like us or whether they are being kind to us merely out of a sense of duty, the wet vagina and the stiff penis function as unambiguous agents of sincerity.
A kiss is pleasurable because of the sensory receptivity of our lips, but a good deal of our excitement has nothing to do with the physical dimension of the act: It stems from the simple realization that someone else likes us quite a lot.