Epistemic vs. Instrumental Rationality: Case of the Leaky Agent

Sup­pose you hire a real-es­tate agent to sell your house. You have to leave town so you give him the au­thor­ity to ne­go­ti­ate with buy­ers on your be­half. The agent is hon­est and hard work­ing. He’ll work as hard to get a good price for your house as if he’s sel­l­ing his own house. But un­for­tu­nately, he’s not very good at keep­ing se­crets. He wants to know what is the min­i­mum amount you’re will­ing to sell the house for so he can do the ne­go­ti­a­tions for you. But you know that if you an­swer him truth­fully, he’s li­able to leak that in­for­ma­tion to buy­ers, giv­ing them a bar­gain­ing ad­van­tage and driv­ing down the ex­pected clos­ing price. What should you do? Pre­sum­ably most of you in this situ­a­tion would give the agent a figure that’s higher than the ac­tual min­i­mum. (How much higher in­volves op­ti­miz­ing a trade­off be­tween the ex­tra money you get if the house sells, ver­sus the prob­a­bil­ity that you can’t find a buyer at the higher fic­tional min­i­mum.)

Now here’s the kicker: that agent is ac­tu­ally your fu­ture self. Would you tell your­self a lie, if you could be­lieve it (per­haps with the help of fu­ture mem­ory mod­ifi­ca­tion tech­nolo­gies), and if you could profit from it?

Edit: Some com­menters have pointed out that this change in “min­i­mum ac­cept­able price” may not be ex­actly a lie. I should have made the ex­am­ple a bit clearer. Let’s say if you fail to sell the house by a cer­tain date, it will be re­posessed by the bank, so the min­i­mum ac­cept­able price is the amount left on your mort­gage, since you’re bet­ter off sel­l­ing the house for any amount above that than not sel­l­ing it. But if buy­ers know that, they can just offer you slightly above the min­i­mum ac­cept­able price. It will help you get a bet­ter bar­gain if you can make your­self be­lieve that the amount left on your mort­gage is higher than it re­ally is. This should be un­am­bi­gously a lie.