“But It Doesn’t Matter”

If you ever find your­self say­ing, “Even if Hy­poth­e­sis H is true, it doesn’t have any de­ci­sion-rele­vant im­pli­ca­tions,” you are ra­tio­nal­iz­ing! The fact that H is in­ter­est­ing enough for you to be con­sid­er­ing the ques­tion at all (it’s not some ar­bi­trary triv­ium like the 1923th bi­nary digit of π, or the low tem­per­a­ture in São Paulo on Septem­ber 17, 1978) means that it must have some rele­vance to the things you care about. It is van­ish­ingly im­prob­a­ble that your op­ti­mal de­ci­sions are go­ing to be the same in wor­lds where H is true and wor­lds where H is false. The fact that you’re tempted to say they’re the same is prob­a­bly be­cause some part of you is afraid of some of the imag­ined con­se­quences of H be­ing true. But H is already true or already false! If you hap­pen to live in a world where H is true, and you make de­ci­sions as if you lived in a world where H is false, you are thereby miss­ing out on all the ex­tra util­ity you would get if you made the H-op­ti­mal de­ci­sions in­stead! If you can figure out ex­actly what you’re afraid of, maybe that will help you work out what the H-op­ti­mal de­ci­sions are. Then you’ll be a bet­ter po­si­tion to suc­cess­fully no­tice which world you ac­tu­ally live in.