"The secret to a stable relationship like ours," she said proudly," is give and take, a real 50/50 balance." I should look at her while she's talking to me, but I'm sneaking peeks at him, checking for a reaction. I know the couple well and you would have to cook the books pretty creatively to call their relationship 50/50. My guess is closer to 90/10. In our circles she's notorious for her demands and expectations. She takes up a lot of space which he supplies with nary a flinch. How does that work? My guess is that it's a 50/50 balance around a 90/10 set point. In other words, they're still negotiating a little give and take, but it's between say, 87/13, and 93/7. He doesn't flinch because he's not wondering about the set point. He's not wondering because the variation around the set point feels easy and balanced, sloshing gently and reliably around even a set point as skewed as theirs'. How are set points negotiated? Let's start by noticing the continuum between business and friend relationships. In business we audit who owes what. In friendship we try not to audit. Love is ideally way over on the friendship side of the continuum, so far over into ignoring who owes what that it's unsafe to love just anyone. You better pick your lover carefully or you'll end up failing to audit a joint account you share with an embezzler. To get to where we can ignore who owes what therefore takes a paradoxical blend of auditing and not auditing, carefully keeping track of who owes what so you can get to where you can afford to ignore who owes what. We'll call this the Auditor's Paradox: It takes auditing to stop auditing. To get safely to a set point where you can say, "who's counting?" you have to count who owes what. Keeping track of who owes what has a lot in common with double-entry bookkeeping. Each partner holds and maintains an intuited ledger; a ledger that registers what each gets and gives with each other. When negotiating set points, partners audit, discussing discrepancies as they arise. For example, when a partner says, "You don't appreciate what I did for you last week," it's the equivalent to "What I did for you last week is recorded in my ledger as accounts receivable, but you don't seem to have it recorded in your ledger as accounts payable." We mark and audit our transactions using the conventional terms of etiquette. For example terms like "please" "thank you," and "sorry" all mean, "I'm registering this transaction as establishing a debt to you, something I will add to my accounts payable, and you can add to your accounts receivable." These terms say, "I hereby acknowledge that I am receiving something from you." They're like receipts. How about invoices? When you say, "Well...OK, here you go," as you grant a favor, it can be like invoicing, like saying "In giving this favor, I'm recording in my accounts receivable a debt you now owe me." But what if instead you say, "not a problem," "no worries" or "don't mention it" as you grant a favor? Those don't sound like invoices. Taken literally they mean something more like "I'm not keeping track of the favor I just granted. You need not register it in your accounts payable, because I'm not registering it in my accounts receivable." What's up with that? Auditing is toxic buzz-kill to friendship and especially to love. Imagine billing your friends for the Thanksgiving dinner you provide them, or giving your partner an itemized list of the expenses you've incurred in your relationship. But given the Auditor's Paradox, auditing is also necessary. We shouldn't pair with someone who systematically cooks the books in his or her favor, so we have to audit some. But we also shouldn't stay with someone who is constantly auditing, so we try to offset auditing's buzz-kill by bestowing romantically lavish acts of kindness, acts that seem t