Mak­ing Be­liefs Pay Rent (in Anti­cip­ated Ex­per­i­ences)

Thus be­gins the an­cient par­able:

If a tree falls in a forest and no one hears it, does it make a sound? One says, “Yes it does, for it makes vi­bra­tions in the air.” Another says, “No it does not, for there is no aud­it­ory pro­cessing in any brain.”

Sup­pose that, after the tree falls, the two walk into the forest to­gether. Will one ex­pect to see the tree fallen to the right, and the other ex­pect to see the tree fallen to the left? Sup­pose that be­fore the tree falls, the two leave a sound re­corder next to the tree. Would one, play­ing back the re­corder, ex­pect to hear some­thing dif­fer­ent from the other? Sup­pose they at­tach an elec­tro­en­ceph­al­o­graph to any brain in the world; would one ex­pect to see a dif­fer­ent trace than the other? Though the two ar­gue, one say­ing “No,” and the other say­ing “Yes,” they do not an­ti­cip­ate any dif­fer­ent ex­per­i­ences. The two think they have dif­fer­ent mod­els of the world, but they have no dif­fer­ence with re­spect to what they ex­pect will hap­pen to them.

It’s tempt­ing to try to elim­in­ate this mis­take class by in­sist­ing that the only le­git­im­ate kind of be­lief is an an­ti­cip­a­tion of sens­ory ex­per­i­ence. But the world does, in fact, con­tain much that is not sensed dir­ectly. We don’t see the atoms un­der­ly­ing the brick, but the atoms are in fact there. There is a floor be­neath your feet, but you don’t ex­per­i­ence the floor dir­ectly; you see the light re­flec­ted from the floor, or rather, you see what your ret­ina and visual cor­tex have pro­cessed of that light. To in­fer the floor from see­ing the floor is to step back into the un­seen causes of ex­per­i­ence. It may seem like a very short and dir­ect step, but it is still a step.

You stand on top of a tall build­ing, next to a grand­father clock with an hour, minute, and tick­ing second hand. In your hand is a bowl­ing ball, and you drop it off the roof. On which tick of the clock will you hear the crash of the bowl­ing ball hit­ting the ground?

To an­swer pre­cisely, you must use be­liefs like Earth’s grav­ity is 9.8 meters per second per second, and This build­ing is around 120 meters tall. These be­liefs are not word­less an­ti­cip­a­tions of a sens­ory ex­per­i­ence; they are verbal-ish, pro­pos­i­tional. It prob­ably does not ex­ag­ger­ate much to de­scribe these two be­liefs as sen­tences made out of words. But these two be­liefs have an in­fer­en­tial con­sequence that is a dir­ect sens­ory an­ti­cip­a­tion—if the clock’s second hand is on the 12 nu­meral when you drop the ball, you an­ti­cip­ate see­ing it on the 1 nu­meral when you hear the crash five seconds later. To an­ti­cip­ate sens­ory ex­per­i­ences as pre­cisely as pos­sible, we must pro­cess be­liefs that are not an­ti­cip­a­tions of sens­ory ex­per­i­ence.

It is a great strength of Homo sapi­ens that we can, bet­ter than any other spe­cies in the world, learn to model the un­seen. It is also one of our great weak points. Hu­mans of­ten be­lieve in things that are not only un­seen but un­real.

The same brain that builds a net­work of in­ferred causes be­hind sens­ory ex­per­i­ence, can also build a net­work of causes that is not con­nec­ted to sens­ory ex­per­i­ence, or poorly con­nec­ted. Al­chem­ists be­lieved that phlo­gis­ton caused fire—we could over­simply their minds by draw­ing a little node labeled “Ph­lo­gis­ton”, and an ar­row from this node to their sens­ory ex­per­i­ence of a crack­ling camp­fire—but this be­lief yiel­ded no ad­vance pre­dic­tions; the link from phlo­gis­ton to ex­per­i­ence was al­ways con­figured after the ex­per­i­ence, rather than con­strain­ing the ex­per­i­ence in ad­vance. Or sup­pose your post­mod­ern Eng­lish pro­fessor teaches you that the fam­ous writer Wulky Wilkin­sen is ac­tu­ally a “post-uto­pian”. What does this mean you should ex­pect from his books? Noth­ing. The be­lief, if you can call it that, doesn’t con­nect to sens­ory ex­per­i­ence at all. But you had bet­ter re­mem­ber the pro­pos­i­tional as­ser­tion that “Wulky Wilkin­sen” has the “post-uto­pian” at­trib­ute, so you can re­gur­git­ate it on the up­com­ing quiz. Like­wise if “post-uto­pi­ans” show “co­lo­nial ali­en­a­tion”; if the quiz asks whether Wulky Wilkin­sen shows co­lo­nial ali­en­a­tion, you’d bet­ter an­swer yes. The be­liefs are con­nec­ted to each other, though still not con­nec­ted to any an­ti­cip­ated ex­per­i­ence.

We can build up whole net­works of be­liefs that are con­nec­ted only to each other—call these “float­ing” be­liefs. It is a uniquely hu­man flaw among an­imal spe­cies, a per­ver­sion of Homo sapi­ens’s abil­ity to build more gen­eral and flex­ible be­lief net­works.

The ra­tion­al­ist vir­tue of em­pir­i­cism con­sists of con­stantly ask­ing which ex­per­i­ences our be­liefs pre­dict—or bet­ter yet, pro­hibit. Do you be­lieve that phlo­gis­ton is the cause of fire? Then what do you ex­pect to see hap­pen, be­cause of that? Do you be­lieve that Wulky Wilkin­sen is a post-uto­pian? Then what do you ex­pect to see be­cause of that? No, not “co­lo­nial ali­en­a­tion”; what ex­per­i­ence will hap­pen to you? Do you be­lieve that if a tree falls in the forest, and no one hears it, it still makes a sound? Then what ex­per­i­ence must there­fore be­fall you?

It is even bet­ter to ask: what ex­per­i­ence must not hap­pen to you? Do you be­lieve that elan vi­tal ex­plains the mys­ter­i­ous alive­ness of liv­ing be­ings? Then what does this be­lief not al­low to hap­pen—what would def­in­itely falsify this be­lief? A null an­swer means that your be­lief does not con­strain ex­per­i­ence; it per­mits any­thing to hap­pen to you. It floats.

When you ar­gue a seem­ingly fac­tual ques­tion, al­ways keep in mind which dif­fer­ence of an­ti­cip­a­tion you are ar­guing about. If you can’t find the dif­fer­ence of an­ti­cip­a­tion, you’re prob­ably ar­guing about la­bels in your be­lief net­work—or even worse, float­ing be­liefs, barnacles on your net­work. If you don’t know what ex­per­i­ences are im­plied by Wulky Wilkin­sen be­ing a post-uto­pian, you can go on ar­guing forever. (You can also pub­lish pa­pers forever.)

Above all, don’t ask what to be­lieve—ask what to an­ti­cip­ate. Every ques­tion of be­lief should flow from a ques­tion of an­ti­cip­a­tion, and that ques­tion of an­ti­cip­a­tion should be the cen­ter of the in­quiry. Every guess of be­lief should be­gin by flow­ing to a spe­cific guess of an­ti­cip­a­tion, and should con­tinue to pay rent in fu­ture an­ti­cip­a­tions. If a be­lief turns dead­beat, evict it.