One of the reasons intimacy and love are not the same thing (although clearly they share some features) is the fact that intimacy is intrinsically reciprocal. It is not a trait or a state. Love, like other emotional states, can be seen as characteristic of an individual, while intimacy is of necessity a relational idea, like conversation. Love fundamentally is a different thing because you can love someone who doesn't love you back and you can also love an idealized or distorted version of the person. This is where love is more like infatuation. For intimacy we need more accurate knowledge of each other and mutuality. Ultimately, unlike love, hate or any other emotion, intimacy exists between rather than within people; you can experience unrequited love, but you cannot experience unrequited intimacy.

Intimacy is often confused with, or subsumed within, love because we associate the strength of feeling and the vulnerability that can be true of both as meaning they are parts of the same experience. Yet we can have love without intimacy and intimacy without love. Lovers can often experience intimacy, of course, but so can friends and even strangers. Equally, lovers can be baffled by a lack of connection.

The need for a reciprocal element to intimacy leads to some controversial claims. As we saw earlier, we often use the term in ways that overextend it, such as saying someone has intimate knowledge of her subject. The word will serve well enough in that context but the intimacy we crave in general needs a knowing partner. Mutual knowledge is a technical concept in logic. It contrasts with individual knowledge, where I know something and you know something. Mutual knowledge takes a crucial additional step: I know that you know that I know.