# Heat vs. Motion

After yes­ter­day’s post, it oc­curred to me that there’s a much sim­pler ex­am­ple of re­duc­tion­ism jump­ing a gap of ap­par­ent-differ­ence-in-kind: the re­duc­tion of heat to mo­tion.

To­day, the equiv­alence of heat and mo­tion may seem too ob­vi­ous in hind­sightev­ery­one says that “heat is mo­tion”, there­fore, it can’t be a “weird” be­lief.

But there was a time when the ki­netic the­ory of heat was a highly con­tro­ver­sial sci­en­tific hy­poth­e­sis, con­trast­ing to be­lief in a caloric fluid that flowed from hot ob­jects to cold ob­jects. Still ear­lier, the main the­ory of heat was “Phlo­gis­ton!

Sup­pose you’d sep­a­rately stud­ied ki­netic the­ory and caloric the­ory. You now know some­thing about ki­net­ics: col­li­sions, elas­tic re­bounds, mo­men­tum, ki­netic en­ergy, grav­ity, in­er­tia, free tra­jec­to­ries. Separately, you know some­thing about heat: Tem­per­a­tures, pres­sures, com­bus­tion, heat flows, en­g­ines, melt­ing, va­por­iza­tion.

Not only is this state of knowl­edge a plau­si­ble one, it is the state of knowl­edge pos­sessed by e.g. Sadi Carnot, who, work­ing strictly from within the caloric the­ory of heat, de­vel­oped the prin­ci­ple of the Carnot cy­cle—a heat en­g­ine of max­i­mum effi­ciency, whose ex­is­tence im­plies the sec­ond law of ther­mo­dy­nam­ics. This in 1824, when ki­net­ics was a highly de­vel­oped sci­ence.

Sup­pose, like Carnot, you know a great deal about ki­net­ics, and a great deal about heat, as sep­a­rate en­tities. Separate en­tities of knowl­edge, that is: your brain has sep­a­rate filing bas­kets for be­liefs about ki­net­ics and be­liefs about heat. But from the in­side, this state of knowl­edge feels like liv­ing in a world of mov­ing things and hot things, a world where mo­tion and heat are in­de­pen­dent prop­er­ties of mat­ter.

Now a Physi­cist From The Fu­ture comes along and tells you: “Where there is heat, there is mo­tion, and vice versa. That’s why, for ex­am­ple, rub­bing things to­gether makes them hot­ter.”

There are (at least) two pos­si­ble in­ter­pre­ta­tions you could at­tach to this state­ment, “Where there is heat, there is mo­tion, and vice versa.”

First, you could sup­pose that heat and mo­tion ex­ist sep­a­rately—that the caloric the­ory is cor­rect—but that among our uni­verse’s phys­i­cal laws is a “bridg­ing law” which states that, where ob­jects are mov­ing quickly, caloric will come into ex­is­tence. And con­versely, an­other bridg­ing law says that caloric can ex­ert pres­sure on things and make them move, which is why a hot­ter gas ex­erts more pres­sure on its en­clo­sure (thus a steam en­g­ine can use steam to drive a pis­ton).

Se­cond, you could sup­pose that heat and mo­tion are, in some as-yet-mys­te­ri­ous sense, the same thing.

“Non­sense,” says Thinker 1, “the words ‘heat’ and ‘mo­tion’ have two differ­ent mean­ings; that is why we have two differ­ent words. We know how to de­ter­mine when we will call an ob­served phe­nomenon ‘heat’—heat can melt things, or make them burst into flame. We know how to de­ter­mine when we will say that an ob­ject is ‘mov­ing quickly’—it changes po­si­tion; and when it crashes, it may de­form, or shat­ter. Heat is con­cerned with change of sub­stance; mo­tion, with change of po­si­tion and shape. To say that these two words have the same mean­ing is sim­ply to con­fuse your­self.”

“Im­pos­si­ble,” says Thinker 2. “It may be that, in our world, heat and mo­tion are as­so­ci­ated by bridg­ing laws, so that it is a law of physics that mo­tion cre­ates caloric, and vice versa. But I can eas­ily imag­ine a world where rub­bing things to­gether does not make them hot­ter, and gases don’t ex­ert more pres­sure at higher tem­per­a­tures. Since there are pos­si­ble wor­lds where heat and mo­tion are not as­so­ci­ated, they must be differ­ent prop­er­ties—this is true a pri­ori.”

Thinker 1 is con­fus­ing the quo­ta­tion and the refer­ent. 2 + 2 = 4, but “2 + 2” ≠ “4“. The string “2 + 2” con­tains 5 char­ac­ters (in­clud­ing whites­pace) and the string “4” con­tains only 1 char­ac­ter. If you type the two strings into a Python in­ter­preter, they yield the same out­put,—> 4. So you can’t con­clude, from look­ing at the strings “2 + 2” and “4″, that just be­cause the strings are differ­ent, they must have differ­ent “mean­ings” rel­a­tive to the Python In­ter­preter.

The words “heat” and “ki­netic en­ergy” can be said to “re­fer to” the same thing, even be­fore we know how heat re­duces to mo­tion, in the sense that we don’t know yet what the refer­ence is, but the refer­ences are in fact the same. You might imag­ine an Ideal­ized Om­ni­scient Science In­ter­preter that would give the same out­put when we typed in “heat” and “ki­netic en­ergy” on the com­mand line.

I talk about the Science In­ter­preter to em­pha­size that, to derefer­ence the poin­ter, you’ve got to step out­side cog­ni­tion. The end re­sult of the derefer­ence is some­thing out there in re­al­ity, not in any­one’s mind. So you can say “real refer­ent” or “ac­tual refer­ent”, but you can’t eval­u­ate the words lo­cally, from the in­side of your own head. You can’t rea­son us­ing the ac­tual heat-refer­ent—if you thought us­ing real heat, think­ing “1 mil­lion Kelvin” would va­por­ize your brain. But, by form­ing a be­lief about your be­lief about heat, you can talk about your be­lief about heat, and say things like “It’s pos­si­ble that my be­lief about heat doesn’t much re­sem­ble real heat.” You can’t ac­tu­ally perform that com­par­i­son right there in your own mind, but you can talk about it.

Hence you can say, “My be­liefs about heat and mo­tion are not the same be­liefs, but it’s pos­si­ble that ac­tual heat and ac­tual mo­tion are the same thing.” It’s just like be­ing able to ac­knowl­edge that “the morn­ing star” and “the evening star” might be the same planet, while also un­der­stand­ing that you can’t de­ter­mine this just by ex­am­in­ing your be­liefs—you’ve got to haul out the telescope.

Thinker 2′s mis­take fol­lows similarly. A physi­cist told him, “Where there is heat, there is mo­tion” and P2 mis­took this for a state­ment of phys­i­cal law: The pres­ence of caloric causes the ex­is­tence of mo­tion. What the physi­cist re­ally means is more akin to an in­fer­en­tial rule: Where you are told there is “heat”, de­duce the pres­ence of “mo­tion”.

From this ba­sic pro­jec­tion of a mul­ti­level model into a mul­ti­level re­al­ity fol­lows an­other, dis­tinct er­ror: the con­fla­tion of con­cep­tual pos­si­bil­ity with log­i­cal pos­si­bil­ity. To Sadi Carnot, it is con­ceiv­able that there could be an­other world where heat and mo­tion are not as­so­ci­ated. To Richard Feyn­man, armed with spe­cific knowl­edge of how to de­rive equa­tions about heat from equa­tions about mo­tion, this idea is not only in­con­ceiv­able, but so wildly in­con­sis­tent as to make one’s head ex­plode.

I should note, in fair­ness to philoso­phers, that there are philoso­phers who have said these things. For ex­am­ple, Hilary Put­nam, writ­ing on the “Twin Earth” thought ex­per­i­ment:

Once we have dis­cov­ered that wa­ter (in the ac­tual world) is H20, noth­ing counts as a pos­si­ble world in which wa­ter isn’t H20. In par­tic­u­lar, if a “log­i­cally pos­si­ble” state­ment is one that holds in some “log­i­cally pos­si­ble world”, it isn’t log­i­cally pos­si­ble that wa­ter isn’t H20.

On the other hand, we can perfectly well imag­ine hav­ing ex­pe­riences that would con­vince us (and that would make it ra­tio­nal to be­lieve that) wa­ter isn’t H20. In that sense, it is con­ceiv­able that wa­ter isn’t H20. It is con­ceiv­able but it isn’t log­i­cally pos­si­ble! Con­ceiv­abil­ity is no proof of log­i­cal pos­si­bil­ity.

It ap­pears to me that “wa­ter” is be­ing used in two differ­ent senses in these two para­graphs—one in which the word “wa­ter” refers to what we type into the Science In­ter­preter, and one in which “wa­ter” refers to what we get out of the Science In­ter­preter when we type “wa­ter” into it. In the first para­graph, Hilary seems to be say­ing that af­ter we do some ex­per­i­ments and find out that wa­ter is H20, wa­ter be­comes au­to­mat­i­cally re­defined to mean H20. But you could co­her­ently hold a differ­ent po­si­tion about whether the word “wa­ter” now means “H20″ or “what­ever is re­ally in that bot­tle next to me”, so long as you use your terms con­sis­tently.

I be­lieve the above has already been said as well? Any­way...

It is quite pos­si­ble for there to be only one thing out-there-in-the-world, but for it to take on suffi­ciently differ­ent forms, and for you your­self to be suffi­ciently ig­no­rant of the re­duc­tion, that it feels like liv­ing in a world con­tain­ing two en­tirely differ­ent things. Knowl­edge con­cern­ing these two differ­ent phe­nom­ena may taught in two differ­ent classes, and stud­ied by two differ­ent aca­demic fields, lo­cated in two differ­ent build­ings of your uni­ver­sity.

You’ve got to put your­self quite a ways back, into a his­tor­i­cally re­al­is­tic frame of mind, to re­mem­ber how differ­ent heat and mo­tion once seemed. Though, de­pend­ing on how much you know to­day, it may not be as hard as all that, if you can look past the pres­sure of con­ven­tion­al­ity (that is, “heat is mo­tion” is an un-weird be­lief, “heat is not mo­tion” is a weird be­lief). I mean, sup­pose that to­mor­row the physi­cists stepped for­ward and said, “Our pop­u­lariza­tions of sci­ence have always con­tained one lie. Ac­tu­ally, heat has noth­ing to do with mo­tion.” Could you prove they were wrong?

Say­ing “Maybe heat and mo­tion are the same thing!” is easy. The difficult part is ex­plain­ing how. It takes a great deal of de­tailed knowl­edge to get your­self to the point where you can no longer con­ceive of a world in which the two phe­nom­ena go sep­a­rate ways. Re­duc­tion isn’t cheap, and that’s why it buys so much.

Or maybe you could say: “Re­duc­tion­ism is easy, re­duc­tion is hard.” But it does kinda help to be a re­duc­tion­ist, I think, when it comes time to go look­ing for a re­duc­tion.

• Con­sider two iden­ti­cal fly­wheels made of iron:

a) starts in room tem­per­a­ture, you ap­ply force and make it spin. b) stands still but you heat it uniformily with sev­eral flames.

Sup­pose that in both cases the same amount of en­ergy has been put into the fly­wheels.

In both cases the atoms are mov­ing in high speed. Now if you look at the fly­wheels with an in­frared cam­era would they look the same? This is not a rethor­i­cal ques­tion.

• Huh, no­body’s an­swered this.

The torched iron would emit more in­frared than the spin­ning iron.

The rea­son is be­cause ther­mal mo­tion isn’t just any ol’ mo­tion—it’s mo­tion that has had time to come to equil­ibrium be­tween al­llll the differ­ent ways the atoms in the solid can move. For ex­am­ple, the first atom could move left, and the sec­ond atom move right, and the third atom move left, and so on. All told there are as many ways for the atoms to move as there are atoms in the solid, which is more than 10^23, which is way more than the measly 1 way of mov­ing that is “all atoms go around the cen­ter.” In or­der to emit in­frared light you need the atoms os­cillat­ing against their neigh­bors at high fre­quency, which is a big chunk of those 10^23 ways the atoms can move, but doesn’t have any­thing to do with “all atoms go around the cen­ter.”

• Non-rhetor­i­cal an­swer: No.

You may now be­gin speak­ing rhetor­i­cally.

• “the con­fla­tion of con­cep­tual pos­si­bil­ity with log­i­cal pos­si­bil­ity. To Sadi Carnot, it is con­ceiv­able that there could be an­other world where heat and mo­tion are not as­so­ci­ated. To Richard Feyn­man, armed with spe­cific knowl­edge of how to de­rive equa­tions about heat from equa­tions about mo­tion, this idea is [...] so wildly in­con­sis­tent as to make one’s head ex­plode.”

Shouldn’t we dis­t­in­guish be­tween log­i­cal and phys­i­cal pos­si­bil­ity? A world in which heat and mo­tion are dis­as­so­ci­ated seems to be im­pos­si­ble in a rather differ­ent way than wor­lds in which the law of non­con­tra­dic­tion is false or 7,497 is prime are im­pos­si­ble.

• Davis, that de­pends on whether you take the word “heat” to re­fer to “what­ever ac­tu­ally melts metal” or “micro­scopic move­ments and col­li­sions of molecules”. See the var­i­ous dis­cus­sions of Hilary Put­nam’s “Twin World” dilemma for more along these lines.

• If we look at some­thing with the naked eye and see “plas­tic” and then look at it again with a su­per-micro­scope and see fun­da­men­tal par­ti­cles whizzing around, why does the sec­ond ob­ser­va­tion dis­prove the first or some­how make it an illu­sion?

Fact 1. This ob­ject, when looked at through the naked eye, looks like X. Fact 2. This ob­ject, when looked at through the micro­scope, looks like Y.

Even af­ter you know Fact 2, Fact 1 is still true. Micro­scopes don’t make liars of our eyes. I think the er­ror is in not ac­cept­ing hu­man limi­ta­tions to be­ing with.

We are limited. We can only know what things look like through this or through that. But most peo­ple for­get this and there­fore state the two facts as “This ob­ject looks like X” and “This ob­ject looks like Y” with X != Y, so they think they have to dis­card one of the facts to avoid a con­tra­dic­tion. Really, they should be care­ful to state the full con­text of what they knew each time.

• I’m still wait­ing for some­one to tell me where the color is, in a uni­verse made of col­or­less el­e­men­tary par­ti­cles.

• The color is in your mind. Your brain cre­ates the sen­sa­tion of var­i­ous col­ors based on the fre­quency of light com­ing into your eyes.

• Tech­ni­cally, cer­tain pho­tons have colours. Our “colour” cat­e­gories are ex­ces­sively broad, but all pho­tons can be de­scribed as hav­ing a par­tic­u­lar colour, or be­ing colourless.

• Heat has to do more with equil­ibrium than ki­net­ics.

• Mitchell, clearly you haven’t looked at http://​​en.wikipe­dia.org/​​wiki/​​Quarks#Color.

Se­ri­ously though, taboo ‘colour’ from your ques­tion. Ex­actly which bit are you still wait­ing to have ex­plained?

• Ben Jones said:

Se­ri­ously though, taboo ‘colour’ from your ques­tion. Ex­actly which bit are you still wait­ing to have ex­plained?

I think you’re taboo­ing overzeal­ously. If I have a bunch of red balls and a bunch of blue balls, and ask 5 peo­ple to par­ti­tion the balls into two sub­sets based on color, I would ex­pect the same re­sult from all 5 peo­ple. How do they do it?

• I can’t speak for the other 4 peo­ple, but I was taught to perform that trick in kinder­garten. They even asked me which color was my fa­vorite. Later, in high school, I learned about the differ­ence be­tween red and blue on the elec­tro­mag­netic spec­trum. And still later, in col­lege, I learned about color per­cep­tion in Psych and Com­pSci classes. For a while, I imag­ined that ev­ery­one had learned the same color facts that I had.

Then I ven­tured into a philos­o­phy class­room, was ex­posed to G.E. Moore talk­ing about “yel­low” and “qualia”, and I came to un­der­stand that not ev­ery­one had the same ed­u­ca­tional ad­van­tages I had.

• The philoph­i­cal ques­tion of qualia has noth­ing to do with how the sen­sa­tion of color gets to your brain. It’s about what it does in your brain that makes you con­scious of it.

• In or­der to an­swer the ques­tion you need to first un­der­stand what color ac­tu­ally is.

Once you do, the an­swer to both your and Mitchell’s ques­tions are im­me­di­ately ob­vi­ous.

• So what is it?

• I was ex­pect­ing you to go dis­cover it for your­self. It’s much bet­ter that way. It re­ally is a “palm to the fore­head” mo­ment.

If you want a fur­ther push, you could start with Wikipe­dia, it has a pretty good ex­pla­na­tion of it.

• Down­voted for “I know some­thing you don’t know, but you’ll one day learn, young grasshop­per” at­ti­tude.

If you have an an­swer, and some­one asks you for it, then if it’s sim­ple enough to an­swer, an­swer it. If you have no an­swer, don’t pre­tend you do.

• Voted up, be­cause you’re ab­solutely right.

• I’m guess­ing you don’t mean the part where it says “com­plex and con­tin­u­ing philo­soph­i­cal dis­pute, see qualia”.

• I’ll be frank, I hon­estly do not un­der­stand where the philo­soph­i­cal dis­pute comes from. It seems in­cred­ibly silly to me.

The idea that a spe­cific wave­length can trig­ger a spe­cific elec­tro-chem­i­cal re­sponse in a spe­cific or­gan, which is then trans­mit­ted to a spe­cific part of the brain which pro­cesses that re­sponse in a spe­cific man­ner, but some­how the men­tal rep­re­sen­ta­tion of such comes out of nowhere is non­sen­si­cal to me. Where would you even come up with such an idea?

Again I’m re­minded of com­puter mon­i­tors. It’s not magic by which they pro­duce light of vary­ing wave­lengths and in­ten­si­ties on the screen, there is a real phys­i­cal pro­cess go­ing on. An elec­tri­cal en­g­ineer could tell you all about in ex­ten­sive de­tail.

Com­put­ers can dis­t­in­guish be­tween var­i­ous col­ors very well, and can even pro­cess those col­ors with­out any light as in­put.

What do com­put­ers “see” when they see color?

• I would rather say that the ob­serv­able con­se­quences of the heat like na­ture of the uni­verse are already in­cluded in the ob­serv­able con­se­quences of the kine­matic like na­ture of the uni­verse, so heat is re­dun­dent in this sence, though still a use­ful idea.

Rely­ing on the po­ten­tial ex­is­tence of an Ideal­ized Om­ni­scient Science In­ter­preter feels a bit too much like di­v­ine rev­e­la­tion for my taste. The differ­ence is rather then say­ing “Aha! This is what has ac­tu­ally been hap­pen­ing all along.” I would say “Aha! This more ac­cu­rately fits my ob­ser­va­tions.”

• Of course it’s pos­si­ble to have heat that’s un­re­lated to molec­u­lar mo­tion. Just con­sider frozen mus­tard or red pep­pers.

Ques­tion: How much of to­day’s psy­chol­ogy will look to fu­ture sci­en­tists like at­tempts to mea­sure the hot­ness of jalapeno pep­pers by ther­mome­ters?

• That’s not heat, that’s pain.

• The heat anal­ogy to con­scious­ness is noth­ing new.

Chalmers ex­plains and re­sponds here.

• Yes, this is old hat. See also my post on Mi­sus­ing Kripke/​Put­nam, which ex­plic­itly ex­plains why the anal­ogy to ‘wa­ter = H2O’ (and similar a pos­te­ri­ori iden­tities, like heat = molec­u­lar mo­tion) is no help to the phys­i­cal­ist here.

• Peter, your ques­tion doesn’t seem to be the right one for illus­trat­ing your con­cern. The qual­i­ta­tive ex­pe­rience of color isn’t nec­es­sary for ex­plain­ing how some­one can par­ti­tion col­ored balls. Ig­nor­ing the qual­i­ta­tive ex­pe­rience, these peo­ple are go­ing through some pro­cess of de­tect­ing differ­ences in the re­flec­tive prop­er­ties of the balls (which they sub­jec­tively ex­pe­rience as hav­ing differ­ent col­ors). We could cre­ate a re­duc­tive ex­pla­na­tion of how the eye de­tects re­flected light, how the brain cat­e­go­rizes re­flec­tive in­ten­si­ties into con­cepts like “bright” “dark” and how the body’s me­chan­ics en­able pick­ing up and drop­ping balls. A ma­chine with no ap­par­ent sub­jec­tive ex­pe­rience could sort the balls. How­ever the ques­tion of qual­i­ta­tive ex­pe­rience in hu­mans would re­main.

We could say “where there is per­cep­tion, de­duce qual­i­ta­tive ex­pe­rience” but this doesn’t ex­plain any­thing. It might help us frame ex­per­i­ments to test for the ex­is­tence of qual­i­ta­tive ex­pe­rience, but one el­e­ment of Chalmer’s ar­gu­ment is that no such ob­jec­tively ver­ifi­able ex­per­i­ment can be cre­ated. It’s also hard to come to terms with the idea that our ball sort­ing robot might be hav­ing qual­i­ta­tive ex­pe­rience.

If we are dis­card­ing solip­sism from our episte­mol­ogy, on what ba­sis do we do so and is that ba­sis philo­soph­i­cally ap­pli­ca­ble to dis­card­ing the idea that that my qual­i­ta­tive ex­pe­rience might be fun­da­men­tally differ­ent from some­one else’s? Just be­cause I can con­ceive of a world in which what I ex­pe­rience as red is in fact ex­pe­rienced by some­one else with no neu­ral/​op­ti­cal flaws as what I would call yel­low doesn’t make that world log­i­cal. I would as­sume that if the ob­ject and light­ing con­di­tions are the same and our neu­ral and op­ti­cal ma­chin­ery was in good or­der that we would both ex­pe­rience the same thing that it is to ex­pe­rience red when look­ing at a red ob­ject. To con­ceive oth­er­wise would be base­less (purely meta­phys­i­cal with no im­pli­ca­tions for re­al­ity).

• [tan­gent] Hi Bran­don, you may find my post on The Prob­lem of Other Minds to be of in­ter­est—note that the usual jus­tifi­ca­tion is to ar­gue in­duc­tively from anal­ogy (oth­ers are ex­ter­nally similar to our­selves, so most likely have similar in­ner lives).

I think you’re right that the di­verse ex­pe­rience hy­poth­e­sis (my red is your yel­low, etc.) is ‘illog­i­cal’, at least in the weak sense of ad hoc or less than perfectly co­her­ent/​rea­son­able. It is log­i­cally pos­si­ble, mind you—there’s no rea­son the would couldn’t have turned out that way, if the laws of na­ture had been differ­ent. But we are gen­er­ally jus­tified in be­liev­ing that re­al­ity is gov­erned by sys­tem­atic laws. That is, a vari­a­tion of Ock­ham’s Ra­zor will pre­vent us from posit­ing un­nec­es­sary ar­bi­trary dis­tinc­tions.

So you’re right that the di­verse ex­pe­rience view is ‘base­less’. But note that it can’t be for the rea­son that it is “purely meta­phys­i­cal with no im­pli­ca­tions for re­al­ity”. For the same could be said of the rea­son­able (and pre­sum­ably true) view that in fact we both ex­pe­rience the same colour qualia when look­ing at a tomato. That too is a ‘meta­phys­i­cal’ view with no sci­en­tific im­pli­ca­tions. But it’s also plainly rea­son­able. So, not all ‘meta­phys­i­cal’ views are on a par. [/​tan­gent]

• I used to lead with the ral­ly­ing cry of “con­ceiv­abil­ity is not log­i­cal pos­si­bil­ity” but af­ter some re­flec­tion came to the con­clu­sion that log­i­cal pos­si­bil­ity is just an ar­bi­trary sub­set of con­ceiv­abil­ity and the en­tire frame­work of “log­i­cal pos­si­bil­ity” should be re­jected out­right. “This is log­i­cally pos­si­ble” car­ries no weight. It is not a thing. It serves no pur­pose and has no known use. By re­ject­ing it what ex­actly do we stand to lose?

• I in­ter­pret “\$SITUATION is log­i­cally pos­si­ble” to mean “\$SITUATION can be mod­eled with­out any nec­es­sary con­tra­dic­tions”; thus, it’s log­i­cally pos­si­ble for en­ergy not to be con­served (if we al­low to change what­ever laws need to change), but not for 21 to be a prime num­ber (within any sys­tem of ar­ith­metic like the ones we’re used to, but then, if we used an­other sys­tem the rele­vant ob­ject/​pred­i­cate wouldn’t be what we mean by “21″/​”prime”) - or, more sig­nifi­cantly, only one of P=NP and P≠NP is log­i­cally pos­si­ble, even though with my knowl­edge I can con­ceive of both.

• There’s a way you could make the heat=mo­tion con­cept much clearer to Carnot. When one stud­ies kine­mat­ics, one gen­er­ally makes the ap­prox­i­ma­tion that macro­scopic bod­ies are rigid, and the mo­tions of the body re­fer to cen­ter of mass mo­tion, or per­haps ro­ta­tion about some axis. If you ex­plain that “heat” refers to the mo­tion of the con­stituent par­ti­cles rel­a­tive to each other, I think a sci­en­tist of Carnot’s day would un­der­stand the idea pretty quickly.

I think this sort of thing might be what peo­ple mean when they talk about a “bridg­ing the­ory”.

• More sig­nifi­cantly, only one of P=NP and P≠NP is log­i­cally pos­si­ble, even though with my knowl­edge I can con­ceive of both.

Couldn’t P=NP and P≠NP both be con­sis­tent with the stan­dard ax­ioms of com­plex­ity the­ory (what­ever they hap­pen to be right now), in the same way that, say, the differ­ent par­allel pos­tu­lates are all con­sis­tent with the rest of the com­monly ac­cepted ax­ioms of ge­om­e­try, or the way that the con­tinuum hy­poth­e­sis is in­de­pen­dent of Zer­melo–Fraenkel set the­ory with the ax­iom of choice?

• Richard: Chalmers’ ar­gu­ment on the ex­am­ple of heat and his claim that Den­net’s con­cep­tion of a vi­tal­ist is imag­i­nary both ap­pear to me to be cor­rect re­sponses to this style of at­tack on the “hard prob­lem of con­scious­ness”.

Un­for­tu­nately, the post “Mi­sus­ing Kripke” seems to me to be hor­ribly con­fused. You as­sert that “No­body thinks that the ‘Twin Earth’ world Put­nam de­scribes is an im­pos­si­ble one. Rather, we still grant the pos­si­bil­ity of the world it­self, but merely re-as­sess how best to de­scribe it.” and that “we can imag­ine a world where wa­tery stuff isn’t truly wa­ter” but in fact, since I ac­tu­ally un­der­stand why wa­ter is wa­tery and NH3, for in­stance, is not, can no more imag­ine a world where wa­tery stuff isn’t H2O than I can a world in which a hand isn’t five fingers and a trunk. I can vaguely imag­ine be­ing con­fused about ei­ther in some rele­vant re­spects if my brain was ma­nipu­lated in a fine enough man­ner, but these sorts of con­fu­sions are re­ally pretty much con­fu­sions about what con­sti­tutes “wa­tery stuff”. In the Ma­trix I could swim in “wa­ter” that was not made of H2O, but on earth I can see “wa­ter” that turns out to be a mirage too. Both are “wa­tery” in a sense, but not in the rele­vant sense of be­ing the same sort of stuff as my body or a snowflake are made of. There are things that are “painy” in some senses but not in other senses as well. For in­stance, the suffer­ing of a char­ac­ter in a movie, of a per­son’s child­hood self in their false mem­o­ries of sa­tanic abuse, or of a prac­ti­tioner of some sorts of masochis­tic acts.

Your claim above that “there’s no rea­son the would couldn’t have turned out that way, if the laws of na­ture had been differ­ent.” is, to my mind, an­other ex­am­ple of this sort of con­fu­sion. You have of­ten pointed out that sci­en­tists don’t gen­er­ally un­der­stand what philoso­phers do, but it seems to me that the con­verse is also true. Might I be so bold as to sug­gest that both groups are stereo­typed on the ba­sis of the differ­ent but in both cases rel­a­tively silly ac­tivi­ties that they both en­gage in dur­ing the 95% or so of the time when they are not both ac­tu­ally do­ing philos­o­phy? The vast ma­jor­ity of, if not all of, the “nat­u­ral laws” sci­en­tists speak of are not ar­bi­trary. It seems very likely to many promi­nent sci­en­tists (Ein­stein, Hawk­ing, etc) that they couldn’t have been differ­ent at all, and cer­tain that they couldn’t be changed in­di­vi­d­u­ally while leav­ing the uni­verse oth­er­wise the same. It’s worth em­pha­siz­ing that the fact that we find our­selves ob­serv­ing a sim­ple and or­derly world (find our­selves to be ob­ser­va­tions of an or­derly world?) in­di­cates that we are not ob­ser­va­tions se­lected ar­bi­trar­ily from an un­ordered set of ob­ser­va­tions (what­ever that would mean in the gen­eral case, Boltz­mann Brains are a sim­ple-to-con­cep­tu­al­ize spe­cial case).

• Oh. Yeah. There is that op­tion.

• Just be­cause I can con­ceive of a world in which what I ex­pe­rience as red is in fact ex­pe­rienced by some­one else with no neu­ral/​op­ti­cal flaws as what I would call yellow

What ‘ex­pe­rience’? What prop­er­ties does this ex­pe­rience have? Let me guess—you can’t tell us.

How do you jus­tify your as­ser­tion that those ex­pe­riences ex­ist? How would you con­vince an hon­est skep­tic that there is more to your per­cep­tion of mixes of differ­ent wave­lengths of light than can be ex­plained by refer­ring to the prop­er­ties of the eye, the sig­nals the eye sends, and the neu­rol­ogy that pro­cesses those sig­nals?

• Richard:

In an ear­lier post of yours I find. “I’d add that mostly ev­ery­one ac­cepts that the laws of na­ture are con­tin­gent, and that there could have been a law ac­cord­ing to which lead would trans­mute into gold. So I’m pre­sup­pos­ing that com­mon back­ground.”

This is definitely not what I as­sume. Rather, what I as­sume is that the laws of na­ture are, from our per­spec­tive, the com­pu­ta­tions that give our ex­pe­rience as their out­put. An emer­gent level of de­scrip­tion of these com­pu­ta­tions is as be­ing “about” var­i­ous fun­da­men­tal par­ti­cles de­scribed by differ­ent equa­tions, but the equa­tions are all there is to say about the par­ti­cles. There is no Aris­totelian “ma­te­rial” which has the “form” de­scribed by the equa­tion of an elec­tron but could have some other “form”, say the equa­tion , there is just the equa­tion, what Chalmers calls, I be­lieve, “pure causal flux”. Maybe some very very com­plex equa­tion (more com­plex than the or­der of this per­ceived mo­ment?) could be stated such that head ex­plodes...

OK, Zom­bie Michael writ­ing, brain stuffed back into skull. Michael’s head ex­ploded from read­ing “Water just is H2O, which is why you can’t have one with­out the other (and this is so re­gard­less of whether the phys­i­cal laws differ. For ex­am­ple, there could be other wor­lds where wa­ter/​H2O isn’t wet)” in the com­ments of the “Mi­sus­ing Kripke” post. It’s a far clearer ex­am­ple of what he was talk­ing about. H20 is short­hand for a lot of math, that is to say a lot of log­i­cal re­la­tion­ships. Wet­ness emerges from that math, which can be un­der­stood as logic, not just as sym­bols on pa­per fol­low­ing sym­bolic ma­nipu­la­tion con­ven­tions. It’s not just a fact, not the teacher’s pass­word, not a pat­tern to learn to rec­og­nize etc. Physics isn’t stamp col­lect­ing.

By the way, let me take the time here to plug “Think­ing Physics” by Lewis Car­rol Ep­stein, not just for Richard but for ev­ery­one here who doubts that the logic of physics can be con­veyed cleanly with­out the for­mal­ism of sym­bolic ma­nipu­la­tion.

• Think­ing Physics is Gedanken Physics—I loved that book, tore through it at some point while I was in high school. I never found any­thing else quite like it.

• To those who ask where colour arises from in a colourless world; Wrong Ques­tion and Mind Pro­jec­tion bonus!

Imag­ine an alien civil­i­sa­tion that has, say, four­teen colours. Cal­ling two ad­ja­cent ones by the same name would be as ridicu­lous to them as some­one here call­ing green and yel­low the same thing. Still want to claim that ‘red’ is part of the ter­ri­tory? There are wave­lengths, and there is the hu­man fac­ulty to tell them apart at suffi­cient in­ter­vals. Any­thing else is map only. There is no red.

Say you taste an ap­ple. You know that the sen­sa­tion you are ex­pe­rienc­ing is due to chem­i­cals in­ter­act­ing with your taste buds. Do you then say ‘I un­der­stand why this hap­pens, but clearly this dis­tinc­tive ap­pley taste is a thing in its own right, which can’t be ex­plained by chem­i­cal in­ter­ac­tions alone. Whither the ap­pley­ness?’?

I hope not. I hope you’d recog­nise that just be­cause evolu­tion has favoured crea­tures that can recog­nise cer­tain com­bi­na­tions of chem­i­cals (by re­mem­ber­ing them as dis­crete ex­pe­riences like ‘ap­pley taste’), or cer­tain wave­lengths of light, doesn’t mean those sub­jec­tive ‘ex­pe­riences’ are part of the ter­ri­tory.

Con­ces­sion: vi­sion is harder to think about than most sen­sa­tions, be­cause it seems so tightly bound to re­al­ity. Easy to think that what’s on the back of your retina is the world.

• Con­ces­sion: vi­sion is harder to think about than most sen­sa­tions, be­cause it seems so tightly bound to re­al­ity. Easy to think that what’s on the back of your retina is the world.

On this point I like to think about gor­geous pho­tographs of neb­u­lae, which have been taken with in­fra-red telescopes.

How can I see them if they are in­fra-red? The pho­tog­ra­phers sim­ply ad­just the wave­lengths into the range that I can per­ceive, so I get to see the beauty of the neb­ula as though I could see into the in­frared spec­trum.

The fact that you can slide red into yel­low into blue just by ad­just­ing the wave­length of light should make it im­me­di­ately ap­par­ent that there is no sub­stan­tive differ­ence be­tween red, yel­low, or blue—only very slight differ­ences in wave­length. We have evolved three types of cones that each re­spond to a spe­cific slice of the elec­tro­mag­netic spec­trum (it is quite nar­row for each), and these are rep­re­sented as en­tirely differ­ent things in our mind for the pur­pose of dis­t­in­guish­ing be­tween them.

So long as your cones and my cones are work­ing equally well, and our vi­sual cor­tex is func­tion­ing equally well, it’s al­most a cer­tainty that blue, yel­low, and red look ex­actly the same in my mind as they do in yours. This is be­cause the elec­tri­cal and chem­i­cal sig­nals will be iden­ti­cal, and they will be pro­cessed in the same man­ner for each of us. It would be a great sur­prise to dis­cover they “seemed” differ­ent.

Many birds, it’s worth not­ing, have a fourth type of cone that cap­tures a slice of EM ra­di­a­tion in the ul­tra­vi­o­let, be­cause most flow­ers re­flect into the UV spec­trum, while most other things do not. This makes dis­t­in­guish­ing flow­ers from non-flow­ers sig­nifi­cantly eas­ier for the birds who feed on them (and the flow­ers who rely on the birds for pol­li­na­tion).

• BTW, Zom­bie Michael, maybe you can help us. Do you feel con­scious? If so, can you tell us whether you’re ac­tu­ally con­scious or just iden­ti­cal in ab­solutely ev­ery way to some­one who’s con­scious, but lack­ing that su­per-spe­cial con­scious­ness-juju?

• Con­ces­sion: vi­sion is harder to think about than most sen­sa­tions, be­cause it seems so tightly bound to re­al­ity. Easy to think that what’s on the back of your retina is the world.
Ac­tu­ally, since we rely upon vi­sion so heav­ily, we know the most about the ‘illu­sions’ it can pro­duce.

No one who has even ca­su­ally stud­ied how vi­sion works can take “see­ing is be­liev­ing” se­ri­ously.

• Imag­ine an alien civil­i­sa­tion that has, say, four­teen colours. Cal­ling two ad­ja­cent ones by the same name would be as ridicu­lous to them as some­one here call­ing green and yel­low the same thing.

I don’t think you need alien civ­i­liza­tions for this. Not all hu­man lan­guages have color words that map 1:1 to English color words. (I seem to re­call that the word for “red” in Korean in­cludes what English speak­ers would call “cop­per”. I could be mis­taken.)

• Just con­sider this...

• I also re­call hear­ing that in Rus­sian, there are sep­a­rate words for “blue” and “light blue”, just as English has a spe­cial word “pink” for “light red”.

• I also re­call hear­ing that in Rus­sian, there are sep­a­rate words for “blue” and “light blue”

If only English had words like azure, sap­phire, smalt, aqua, turquoise, per­iwin­kle, iris, cerulean, ul­tra­marine, verdi­gris, wa­ter­spout, zaf­fre or cyan to dis­t­in­guish such nu­ances of colour! Of course, the pre­cise bound­aries be­tween the var­i­ous ar­eas of RGB that are given a la­bel and com­monly em­pha­sised in speech will vary dra­mat­i­cally be­tween cul­tures.

• The differ­ence is that, in English, “cyan”, like your other listed ex­am­ples ex­cept the ones that I think are ac­tu­ally green or pur­ple, is a kind of blue (like sepia is a kind of brown, ca­nary is a kind of yel­low, etc.), while “pink” is not a kind of red. In Rus­sian, gol­ubuy is not a kind of siniy, and vice versa.

I think color words in lan­guages are re­ally in­ter­est­ing. Some lan­guages have only three very ba­sic ones that aren’t kinds of any­thing else, and these tend to be trans­lated as “black”, “white”, and “red”—dark, light, and bright col­ors. (They trans­late the bright color as “red” be­cause if you have lots of ob­jects in the room and ask some­one who speaks this lan­guage to point to the best ex­am­ple of that color, they’ll pick some­thing bright red.) Th­ese three words are priv­ileged in English too: they’re the only ones we mod­ify with -en to in­di­cate that some­thing is be­com­ing more that color (red­den, blacken, whiten—never bluen or gree­nen).

• The differ­ence is that, in English, “cyan”, like your other listed ex­am­ples ex­cept the ones that I think are ac­tu­ally green or pur­ple, is a kind of blue

“Cyan” is one of the least “blue” on the list and I al­most omit­ted it. Th­ese days I’d even tend to con­sider some) of those oth­ers “shades of cyan”. Too much study of web de­sign tends to cor­rupt per­cep­tion the same way na­tive lan­guage does.

I think color words in lan­guages are re­ally in­ter­est­ing.

Cer­tainly. Words for other com­mon con­cepts op­er­ate the same way, fram­ing the way we think and in­fluenc­ing the way we slice up re­al­ity. But with col­ors the differ­ences are far eas­ier to study. What can­not be seen with a glance we can quan­tify with a digi­tal cam­era.

• I think it’s rea­son­ably likely that the gen­eral pop­u­la­tion of English speak­ers will con­sider cyan its own thing af­ter a while, in large part for the rea­son you men­tion.

• I think it’s rea­son­ably likely that the gen­eral pop­u­la­tion of English speak­ers will con­sider cyan its own thing af­ter a while, in large part for the rea­son you men­tion.

Prob­a­bly, get­ting in­cluded in the 16 colour palette com­put­ers used at times and be­ing the name for one of the sub­trac­tive pri­mary colours brings it up a bit in pop­u­lar­ity.

• There was an ex­per­i­ment done where par­ti­ci­pants were shown two shades of blue and asked if they were both the same, or slightly differ­ent. When the two shades of blue fell on differ­ent sides of the gol­uboy/​siniy di­vide, Rus­sian-speak­ers were much bet­ter than English speak­ers at dis­t­in­guish­ing them, but they were no bet­ter when both would be gol­uboy or both siniy. Lan­guage dis­tinc­tions do have cog­ni­tive con­se­quences.

• Speak­ing Rus­sian is far from the only rele­vant differ­ence be­tween Rus­sian-speak­ers and non-Rus­sian-speak­ers. What ex­per­i­ment are you refer­ring to, speci­fi­cally?

• Thank you.

• Stan­dard causal re­ver­sal: In Soviet Rus­sia, biolog­i­cal colour dis­tinc­tion causes lin­guis­tic colour dis­tinc­tion!

• How of­ten are most of those used? I rec­og­nize most, but I’ve prob­a­bly used… five of them in the past year, and I thought verdi­gris was green. -_-

• How of­ten are most of those used?

About half of them are used enough to be con­sid­ered ‘words’ not ‘scrab­ble words’ ac­cord­ing to my ad hoc clas­sifi­ca­tion scheme.

• Dunno about Rus­sian, but He­brew has them for sure—“T’khelet” means “Light blue”, “Kakhol” means “blue”. I know quite a few bil­in­gual ~5yo kids, who, if they’re wear­ing a light blue T-shirt, will scream at you if you say “you have a Kakhol T-shirt” in He­brew, but will hap­pily agree they are wear­ing a “blue” T-shirt—thus show­ing that suffi­cient lack of re­flec­tivity can have two con­flict­ing vi­sion sys­tems in the same in­di­vi­d­ual. (BTW—“light blue” is just an ap­prox­i­ma­tion, it’s a spe­cific shade of light blue).

• Ital­ian has az­zurro for ‘light blue’, but nowa­days it’s not that un­usual to use blu for that colour when the differ­ence doesn’t mat­ter. (I was think­ing that this might be a rel­a­tively re­cent in­fluence of English blue, then I re­mem­bered about a fa­mous mid-20th-cen­tury song which refers to the sky as blu.)

two con­flict­ing vi­sion systems

I don’t think that nec­es­sar­ily fol­lows.

• In Span­ish there also a word for light blue, “ce­leste” (et­y­molog­i­cally re­lated to “sky”), and how ap­pro­pri­ate it is to say just “azul” (blue) in­stead of “ce­leste” de­pends on con­text. For ex­am­ple, an Ar­gen­tine would never call their flag “azul y blanca” (blue and white) since they are taught from child­hood that it is “ce­leste y blanca”. But they wouldn’t mind say­ing the sky on a clear day is ei­ther “azul” or “ce­leste”. A same piece of light blue cloth might be called “ce­leste” in some oc­ca­sions, and “azul” in oth­ers—for ex­am­ple if one just wants to con­trast it with a red one.

• Yeah, in flags, foot­ball jer­seys, etc. Ital­ian is more pre­cise too, us­ing blu only for royal blue or darker, ce­leste for sky blue or lighter, and az­zurro for in­ter­me­di­ate shades of blue.

(I think I saw a list of English—Ital­ian ‘false friends’ which listed blu/​blue as false friends, say­ing that It. blu cor­re­sponds to Engl. navy blue and Engl. blue cor­re­sponds to It. az­zurro! In some spe­cific con­texts that might well be/​have been the case, but I don’t think there are that many peo­ple left who would nor­mally use az­zurro for (say) Uno cards, let alone peo­ple who would con­sider it ex­ceed­ingly weird if you called such a card blu.)

• Yup! In Rus­sian, dark blue is “gol­ubuy” and light blue is “siniy”.

• That’s back­wards. Apolo­gies if this re­sponse is too late for you to care.

• Doesn’t that make writ­ing fan­tasy very hard? Wouldn’t it au­to­mat­i­cally turn into Hard Sci-Fi?

• You should see how he does Harry Pot­ter!

(I think it’s bet­ter than the origi­nal, ev­ery night I hope for a new chap­ter, this is prac­ti­cally tor­ture!)

• I don’t mean to be pedan­tic, but why do you write “H20” in­stead of “H2O?”

• I’ve searched all those com­ments be­cause I couldn’t be­lieve I’m the only one both­ered by that. The differ­ence is ac­tu­ally hardly triv­ial; “H20” sug­gests there is a molecule made from 20 con­nected hy­dro­gen atoms! The miss­ing sub­script doesn’t help (isn’t there a way to make sub­script the num­ber?). Of course I know it wasn’t de­liber­ate, and I guess no reader would in­ter­pret is as any­thing else but “wa­ter”. For the sake of com­ple­tion I would ap­pre­ci­ate an edit, though.

• Fwiw, all html or for­mat­ting aside, there’s a fairly well-sup­ported uni­code sub­script 2.

Water has the chem­i­cal for­mula H₂O. Su­gar is C₆H₁₂O₆. See them all here

• Ahhh now I’ve seen it I can’t un­see it.

• For me this ar­ti­cle is re­ally ac­tual since I’ve caught my­self few times already think­ing about pretty this re­la­tion be­tween heat and mo­tion. I am liter­ate and ed­u­cated per­son, I’ve even been learn­ing math BUT nowa­days I am try­ing to re­think all these stuff which is just packed in my head un­der la­bels similar to “heat vs mo­tion”. So ac­tu­ally it is not that hard for me in 2015 to think that heat and mo­tion are prob­a­bly differ­ent con­cepts :) I just know that I need to re­ally think a lot and re-learn the ba­sics in a proper way, not just re-read­ing books again but re­ally “in­vent­ing” the sub­ject for my­self. And re­gard­ing ex­pla­na­tion vs un­der­stand­ing, I’ve read a joke re­cently: two an­a­lysts are hav­ing a lunch and one tells “hey, do you un­der­stand the situ­a­tion on the mid­dle east, what’s go­ing on there?”. And the other one replies “I can ex­plain you, sure”. Then the first guys tells “I can ex­plain this to any­one in this room as well, but I have ac­tu­ally asked if you UNDERSTAND it”.