Seeing Red: Dissolving Mary’s Room and Qualia

Essen­tial Back­ground: Dis­solv­ing the Question

How could we fully ex­plain the differ­ence be­tween red and green to a col­or­blind per­son?

Well, we could of course draw the anal­ogy be­tween col­ors of the spec­trum and tones of sound; have them learn which ob­jects are typ­i­cally green and which are typ­i­cally red (or bet­ter yet, give them a video cam­era with a red filter to look through); ex­plain many of the poli­ti­cal, cul­tural and emo­tional as­so­ci­a­tions of red and green, and so forth… but it seems that the ac­tual differ­ence be­tween our ex­pe­rience of red­ness and our ex­pe­rience of green­ness is some­thing much harder to con­vey. If we fo­cus in on that as­pect of ex­pe­rience, we end up with the clas­sic philo­soph­i­cal con­cept of qualia, and the fa­mous thought ex­per­i­ment known as Mary’s Room1.

Mary is a brilli­ant neu­ro­scien­tist who has been col­or­blind from birth (due to a retina prob­lem; her vi­sual cor­tex would work nor­mally if it were given the color in­put). She’s an ex­pert on the elec­tro­mag­netic spec­trum, op­tics, and the sci­ence of color vi­sion. We can pos­tu­late, since this is a thought ex­per­i­ment, that she knows and fully un­der­stands ev­ery phys­i­cal fact in­volved in color vi­sion; she knows pre­cisely what hap­pens, on var­i­ous lev­els, when the hu­man eye sees red (and the op­tic nerve trans­mits par­tic­u­lar types of sig­nals, and the vi­sual cor­tex pro­cesses these sig­nals, etc).

One day, Mary gets an op­er­a­tion that fixes her reti­nas, so that she fi­nally sees in color for the first time. And when she wakes up, she looks at an ap­ple and ex­claims, “Oh! So that’s what red ac­tu­ally looks like.”2

Now, this ex­cla­ma­tion poses a challenge to any phys­i­cal re­duc­tion­ist ac­count of sub­jec­tive ex­pe­rience. For if the qualia of see­ing red could be re­duced to a col­lec­tion of ba­sic facts about the phys­i­cal world, then Mary would have learned those facts ear­lier and wouldn’t learn any­thing ex­tra now– but of course it seems that she re­ally does learn some­thing when she sees red for the first time. This is not merely the god-of-the-gaps ar­gu­ment that we haven’t yet found a full re­duc­tion­ist ex­pla­na­tion of sub­jec­tive ex­pe­rience, but an in­tu­itive proof that no such ex­pla­na­tion would be com­plete.

The ar­gu­ment in aca­demic philos­o­phy over Mary’s Room re­mains un­set­tled to this day (though it has an in­ter­est­ing his­tory, in­clud­ing a change of mind on the part of its origi­na­tor). If we ig­nore the topic of sub­jec­tive ex­pe­rience, the ar­gu­ments for re­duc­tion­ism ap­pear to be quite over­whelming; so why does this ob­jec­tion, in a do­main in which our ig­no­rance is so vast3, seem so difficult for re­duc­tion­ists to con­vinc­ingly re­ject?

Veter­ans of this blog will know where I’m go­ing: a ques­tion like this needs to be dis­solved, not merely an­swered.

That is, rather than just re­hash­ing the philo­soph­i­cal ar­gu­ments about whether and in what sense qualia ex­ist4, as plenty of philoso­phers have done with­out reach­ing con­sen­sus, we might in­stead ask where our thoughts about qualia come from, and search for a sim­plified ver­sion of the cog­ni­tive al­gorithm be­hind (our ex­pec­ta­tion of) Mary’s re­ac­tion. The great thing about this al­ter­na­tive query is that it’s likely to ac­tu­ally have an an­swer, and that this an­swer can help us in our think­ing about the origi­nal ques­tion.

Eliezer in­tro­duced this ap­proach in his dis­cus­sion of clas­si­cal defi­ni­tional dis­putes and later on in the se­quence on free will, and (in­de­pen­dently, it seems) Gary Drescher re­lied on it in his ex­cel­lent book Good and Real to ac­count for a num­ber of ap­par­ent para­doxes, but it seems that aca­demic philoso­phers haven’t yet taken to the idea. Essen­tially, it brings to the philos­o­phy of mind an ap­proach that is stan­dard in the math­e­mat­i­cal sci­ences: if there’s a phe­nomenon we don’t un­der­stand, it usu­ally helps to find a sim­pler model that ex­hibits the same phe­nomenon, and figure out how ex­actly it arises in that model.

Model­ing Qualia

Our goal, then, is to build a model of a mind that would have an analo­gous re­ac­tion for a gen­uine rea­son5 when placed in a sce­nario like Mary’s Room. We don’t need this model to en­cap­su­late the full struc­ture of hu­man sub­jec­tive ex­pe­rience, just enough to see where the Mary’s Room ar­gu­ment pulls a sleight of hand.

What kinds of fea­tures might our model re­quire in or­der to qual­ify? Since the ar­gu­ment re­lies on the no­tions of learn­ing and di­rect ex­pe­rience, we will cer­tainly need to in­cor­po­rate these. Another fac­tor which is not im­me­di­ately rele­vant, but which I ar­gue is vi­tal, is that our model must des­ig­nate some smaller part of it­self as the “con­scious” mind, and have much of its ac­tivity take place out­side of that part.

Now, why should the con­scious/​un­con­scious di­vide mat­ter to the ex­pe­rience of qualia? Firstly, we note that our qualia feel in­ef­fable to us: that is, it seems like we know their na­ture very well but could never ad­e­quately com­mu­ni­cate or ar­tic­u­late it. If we’re think­ing like a cog­ni­tive sci­en­tist, we might hy­poth­e­size that an un­con­scious part of the mind knows some­thing more fully while the con­scious mind, bet­ter suited to us­ing lan­guage, lacks ac­cess to the full knowl­edge6.

Se­condly, there’s an in­ter­est­ing pat­tern to our in­tu­itions about qualia: we only get this feel­ing of in­ef­fa­bil­ity about men­tal events that we’re con­scious of, but which are mostly pro­cessed sub­con­sciously. For ex­am­ple, we don’t ex­pe­rience the feel­ing of in­ef­fa­bil­ity for some­thing like count­ing, which hap­pens con­sciously (above a thresh­old of five or six). If Mary had never counted more than 100 ob­jects be­fore, and to­day she counted 113 sheep in a field, we wouldn’t ex­pect her to ex­claim “Oh, so that’s what 113 looks like!”

In the other di­rec­tion, there’s a lot of un­con­scious pro­cess­ing that goes into the pro­cess of di­ges­tion, but un­less we get sick, the in­ter­me­di­ate steps don’t gen­er­ally rise to con­scious aware­ness. If Mary had never had pineap­ple be­fore, she might well ex­tol the qualia of its taste, but not that of its prop­er­ties as it nav­i­gates her small in­tes­tine. You could think of these as hid­den qualia, per­haps, but it doesn’t in­tu­itively feel like there’s some­thing ex­tra to be ex­plained the way there is with red­ness.

Of course, there are plenty of other fea­tures we might nom­i­nate for in­clu­sion in our model, but as it turns out, we can get a long way with just these two. In the next post, I’ll in­tro­duce Martha, a sim­ple model of a learn­ing mind with a con­scious/​un­con­scious dis­tinc­tion, and in the third post I’ll show how Martha re­acts in the situ­a­tion of Mary’s Room, and how this re­ac­tion arises in a non-mys­te­ri­ous way. Even with­out claiming that Martha is a good analogue of the hu­man mind, this will suffice to show why Mary’s Room is not a log­i­cally valid ar­gu­ment against re­duc­tion­ism, since if it were then it would equally ap­ply to Martha. And if we start to see a bit of our­selves in Martha af­ter all, so much the bet­ter for our un­der­stand­ing of qualia...



One could rea­son­ably ask what makes my at­tempt spe­cial on such a well-ar­gued topic, given that I’m not cre­den­tialed as a philoso­pher. First, I’d re­it­er­ate that aca­demic philoso­phers re­ally haven’t started to use the con­cept of dis­solv­ing a ques­tion- I don’t think Daniel Den­nett, for in­stance, ever ex­plored this train of thought. And sec­ondly, of those who do try and map cog­ni­tive al­gorithms within philos­o­phy of mind, Eliezer hasn’t tack­led qualia in this way, while Gary Drescher gives them short shrift in Good and Real. (The lat­ter es­sen­tially makes Den­nett’s ar­gu­ment that with enough self-knowl­edge qualia wouldn’t be in­ef­fable. But in my mind this fails to re­ally dis­solve the ques­tion- see my foot­note 4.)


1. The ar­gu­ment is called “Mary’s Room” be­cause the origi­nal ver­sion (due to Frank Jack­son) posited that Mary had perfectly nor­mal vi­sion but hap­pened to be raised and ed­u­cated in a perfectly grayscale en­vi­ron­ment, and one day stepped out into the col­or­ful world like Dorothy in The Wizard of Oz. I pre­fer the more plau­si­ble and philo­soph­i­cally equiv­a­lent var­i­ant dis­cussed above, al­though it drifts away from the et­y­mol­ogy of the ar­gu­ment’s name.

2. Iron­i­cally, it was a green ap­ple rather than a red one, but Mary soon re­al­ized and rec­tified her er­ror. The point stands.

3. In gen­eral, an im­por­tant ra­tio­nal­ist heuris­tic is to not draw far-reach­ing con­clu­sions from an in­tu­itively plau­si­ble ar­gu­ment about a sub­ject (like sub­jec­tive ex­pe­rience) which you find ex­tremely con­fus­ing.

4. Be­fore we move on, though, one key re­duc­tion­ist re­ply to Mary’s Room is that ei­ther qualia have phys­i­cal effects (like caus­ing Mary to say “Oh!”) or they don’t. If they do, then ei­ther they re­duce to or­di­nary physics or you could ex­pect to find vi­o­la­tions of phys­i­cal law in the hu­man brain, which few mod­ern philoso­phers would dare to bet on. And if they don’t have any phys­i­cal effects, then some­how what­ever causes her to say “Oh!” has noth­ing to do with her ac­tual ex­pe­rience of red­ness, which is an ex­cep­tion­ally weird stance if you pon­der it for a mo­ment; read the zom­bie se­quence if you’re cu­ri­ous.

Fur­ther­more, one could ob­ject (as Den­nett does) that Mary’s Room, like Searle’s Chi­nese Room, is play­ing sleight of hand with im­pos­si­ble lev­els of knowl­edge for a hu­man, and that an agent who could re­ally han­dle such mas­sive quan­tities of in­for­ma­tion re­ally wouldn’t learn any­thing new when fi­nally hav­ing the ex­pe­rience. But to me this is an un­satis­fy­ing ob­jec­tion, be­cause we don’t ex­pect to see the effect of the ex­pe­rience diminish sig­nifi­cantly as we in­crease her level of un­der­stand­ing within hu­man bounds– and at most, this ob­jec­tion pro­vides a plau­si­ble es­cape from the ar­gu­ment rather than a re­fu­ta­tion.

5. (and not, for in­stance, be­cause we pro­grammed in that spe­cific re­ac­tion on its own)

6. In­deed, the vast ma­jor­ity of vi­sual pro­cess­ing- es­ti­mat­ing dis­tances, dis­t­in­guish­ing ob­jects, even iden­ti­fy­ing col­ors- is done sub­con­sciously; that’s why know­ing that some­thing is an op­ti­cal illu­sion doesn’t make you stop see­ing the illu­sion. Steven Pinker’s How the Mind Works con­tains a trea­sure trove of ex­am­ples on this sub­ject.