Disputing Definitions

I have watched more than one con­ver­sa­tion—even con­ver­sa­tions sup­pos­edly about cog­ni­tive sci­ence—go the route of dis­put­ing over defi­ni­tions. Tak­ing the clas­sic ex­am­ple to be “If a tree falls in a for­est, and no one hears it, does it make a sound?“, the dis­pute of­ten fol­lows a course like this:

If a tree falls in the for­est, and no one hears it, does it make a sound?

Albert: “Of course it does. What kind of silly ques­tion is that? Every time I’ve listened to a tree fall, it made a sound, so I’ll guess that other trees fal­ling also make sounds. I don’t be­lieve the world changes around when I’m not look­ing.”

Barry: “Wait a minute. If no one hears it, how can it be a sound?”

In this ex­am­ple, Barry is ar­gu­ing with Albert be­cause of a gen­uinely differ­ent in­tu­ition about what con­sti­tutes a sound. But there’s more than one way the Stan­dard Dis­pute can start. Barry could have a mo­tive for re­ject­ing Albert’s con­clu­sion. Or Barry could be a skep­tic who, upon hear­ing Albert’s ar­gu­ment, re­flex­ively scru­ti­nized it for pos­si­ble log­i­cal flaws; and then, on find­ing a coun­ter­ar­gu­ment, au­to­mat­i­cally ac­cepted it with­out ap­ply­ing a sec­ond layer of search for a counter-coun­ter­ar­gu­ment; thereby ar­gu­ing him­self into the op­po­site po­si­tion. This doesn’t re­quire that Barry’s prior in­tu­ition—the in­tu­ition Barry would have had, if we’d asked him be­fore Albert spoke—have differed from Albert’s.

Well, if Barry didn’t have a differ­ing in­tu­ition be­fore, he sure has one now.

Albert: “What do you mean, there’s no sound? The tree’s roots snap, the trunk comes crash­ing down and hits the ground. This gen­er­ates vibra­tions that travel through the ground and the air. That’s where the en­ergy of the fall goes, into heat and sound. Are you say­ing that if peo­ple leave the for­est, the tree vi­o­lates con­ser­va­tion of en­ergy?”

Barry: “But no one hears any­thing. If there are no hu­mans in the for­est, or, for the sake of ar­gu­ment, any­thing else with a com­plex ner­vous sys­tem ca­pa­ble of ‘hear­ing’, then no one hears a sound.”

Albert and Barry re­cruit ar­gu­ments that feel like sup­port for their re­spec­tive po­si­tions, de­scribing in more de­tail the thoughts that caused their “sound”-de­tec­tors to fire or stay silent. But so far the con­ver­sa­tion has still fo­cused on the for­est, rather than defi­ni­tions. And note that they don’t ac­tu­ally dis­agree on any­thing that hap­pens in the for­est.

Albert: “This is the dumb­est ar­gu­ment I’ve ever been in. You’re a nid­dlewick­ing fal­lumph­ing pick­le­plumber.”

Barry: “Yeah? Well, you look like your face caught on fire and some­one put it out with a shovel.”

In­sult has been proffered and ac­cepted; now nei­ther party can back down with­out los­ing face. Tech­ni­cally, this isn’t part of the ar­gu­ment, as ra­tio­nal­ists ac­count such things; but it’s such an im­por­tant part of the Stan­dard Dis­pute that I’m in­clud­ing it any­way.

Albert: “The tree pro­duces acous­tic vibra­tions. By defi­ni­tion, that is a sound.”

Barry: “No one hears any­thing. By defi­ni­tion, that is not a sound.”

The ar­gu­ment starts shift­ing to fo­cus on defi­ni­tions. When­ever you feel tempted to say the words “by defi­ni­tion” in an ar­gu­ment that is not liter­ally about pure math­e­mat­ics, re­mem­ber that any­thing which is true “by defi­ni­tion” is true in all pos­si­ble wor­lds, and so ob­serv­ing its truth can never con­strain which world you live in.

Albert: “My com­puter’s micro­phone can record a sound with­out any­one be­ing around to hear it, store it as a file, and it’s called a ‘sound file’. And what’s stored in the file is the pat­tern of vibra­tions in air, not the pat­tern of neu­ral firings in any­one’s brain. ‘Sound’ means a pat­tern of vibra­tions.”

Albert de­ploys an ar­gu­ment that feels like sup­port for the word “sound” hav­ing a par­tic­u­lar mean­ing. This is a differ­ent kind of ques­tion from whether acous­tic vibra­tions take place in a for­est—but the shift usu­ally passes un­no­ticed.

Barry: “Oh, yeah? Let’s just see if the dic­tio­nary agrees with you.”

There’s a lot of things I could be cu­ri­ous about in the fal­ling-tree sce­nario. I could go into the for­est and look at trees, or learn how to de­rive the wave equa­tion for changes of air pres­sure, or ex­am­ine the anatomy of an ear, or study the neu­roanatomy of the au­di­tory cor­tex. In­stead of do­ing any of these things, I am to con­sult a dic­tio­nary, ap­par­ently. Why? Are the ed­i­tors of the dic­tio­nary ex­pert botanists, ex­pert physi­cists, ex­pert neu­ro­scien­tists? Look­ing in an en­cy­clo­pe­dia might make sense, but why a dic­tio­nary?

Albert: “Hah! Defi­ni­tion 2c in Mer­riam-Web­ster: ‘Sound: Me­chan­i­cal ra­di­ant en­ergy that is trans­mit­ted by lon­gi­tu­di­nal pres­sure waves in a ma­te­rial medium (as air).’”

Barry: “Hah! Defi­ni­tion 2b in Mer­riam-Web­ster: ‘Sound: The sen­sa­tion per­ceived by the sense of hear­ing.’”

Albert and Barry, cho­rus: “Con­sarned dic­tio­nary! This doesn’t help at all!”

Dic­tionary ed­i­tors are his­to­ri­ans of us­age, not leg­is­la­tors of lan­guage. Dic­tionary ed­i­tors find words in cur­rent us­age, then write down the words next to (a small part of) what peo­ple seem to mean by them. If there’s more than one us­age, the ed­i­tors write down more than one defi­ni­tion.

Albert: “Look, sup­pose that I left a micro­phone in the for­est and recorded the pat­tern of the acous­tic vibra­tions of the tree fal­ling. If I played that back to some­one, they’d call it a ‘sound’! That’s the com­mon us­age! Don’t go around mak­ing up your own wacky defi­ni­tions!”

Barry: “One, I can define a word any way I like so long as I use it con­sis­tently. Two, the mean­ing I gave was in the dic­tio­nary. Three, who gave you the right to de­cide what is or isn’t com­mon us­age?”

There’s quite a lot of ra­tio­nal­ity er­rors in the Stan­dard Dis­pute. Some of them I’ve already cov­ered, and some of them I’ve yet to cover; like­wise the reme­dies.

But for now, I would just like to point out—in a mourn­ful sort of way—that Albert and Barry seem to agree on vir­tu­ally ev­ery ques­tion of what is ac­tu­ally go­ing on in­side the for­est, and yet it doesn’t seem to gen­er­ate any feel­ing of agree­ment.

Ar­gu­ing about defi­ni­tions is a gar­den path; peo­ple wouldn’t go down the path if they saw at the out­set where it led. If you asked Albert (Barry) why he’s still ar­gu­ing, he’d prob­a­bly say some­thing like: “Barry (Albert) is try­ing to sneak in his own defi­ni­tion of ‘sound’, the scur­vey scoundrel, to sup­port his ridicu­lous point; and I’m here to defend the stan­dard defi­ni­tion.”

But sup­pose I went back in time to be­fore the start of the ar­gu­ment:

(Eliezer ap­pears from nowhere in a pe­cu­liar con­veyance that looks just like the time ma­chine from the origi­nal ‘The Time Ma­chine’ movie.)

Barry: “Gosh! A time trav­eler!”

Eliezer: “I am a trav­eler from the fu­ture! Hear my words! I have trav­eled far into the past—around fif­teen min­utes—”

Albert: “Fif­teen min­utes?

Eliezer: “—to bring you this mes­sage!”

(There is a pause of mixed con­fu­sion and ex­pec­tancy.)

Eliezer: “Do you think that ‘sound’ should be defined to re­quire both acous­tic vibra­tions (pres­sure waves in air) and also au­di­tory ex­pe­riences (some­one to listen to the sound), or should ‘sound’ be defined as mean­ing only acous­tic vibra­tions, or only au­di­tory ex­pe­rience?”

Barry: “You went back in time to ask us that?

Eliezer: “My pur­poses are my own! An­swer!”

Albert: “Well… I don’t see why it would mat­ter. You can pick any defi­ni­tion so long as you use it con­sis­tently.”

Barry: “Flip a coin. Er, flip a coin twice.”

Eliezer: “Per­son­ally I’d say that if the is­sue arises, both sides should switch to de­scribing the event in un­am­bigu­ous lower-level con­stituents, like acous­tic vibra­tions or au­di­tory ex­pe­riences. Or each side could des­ig­nate a new word, like ‘alber­zle’ and ‘bar­gu­lum’, to use for what they re­spec­tively used to call ‘sound’; and then both sides could use the new words con­sis­tently. That way nei­ther side has to back down or lose face, but they can still com­mu­ni­cate. And of course you should try to keep track, at all times, of some testable propo­si­tion that the ar­gu­ment is ac­tu­ally about. Does that sound right to you?”

Albert: “I guess...”

Barry: “Why are we talk­ing about this?”

Eliezer: “To pre­serve your friend­ship against a con­tin­gency you will, now, never know. For the fu­ture has already changed!”

(Eliezer and the ma­chine van­ish in a puff of smoke.)

Barry: “Where were we again?”

Albert: “Oh, yeah: If a tree falls in the for­est, and no one hears it, does it make a sound?”

Barry: “It makes an alber­zle but not a bar­gu­lum. What’s the next ques­tion?”

This rem­edy doesn’t de­stroy ev­ery dis­pute over cat­e­go­riza­tions. But it de­stroys a sub­stan­tial frac­tion.