Feser Nagelista

Nagelin Mind and Cosmos -teos on jo ehtinyt herättää keskustelua. Edward Feser kirjoittaa parhaillaan sarjaa Nagelista blogissaan. Ensimmäisessä postauksessaan hän antaa lyhyen arvion Nagelin kirjasta omasta aristoteelisesta perspektiivistään; toisessa osassa Feser puolustaa Nagelia Brian Leiterin ja Michael Weisbergin varsin aneemiselta kritiikiltä; kolmannessa Feser on Nagelin puolella Elliot Soberia vastaan; neljännessä kirjoituksessaan Feser kritisoi Alva Noen Nagel-arviota; ja viimeisimmässä osassa Feser puolustaa Nagelia John Duprén hyvin epäreilulta kritiikiltä, minkä hän antaa Notre Dame Philosophical Reviews -arviossaan Nagelin kirjasta. Lisää osia tässä Feserin ”Nagel and his critics” -sarjassa voi vielä olla tulossa. Käykää ihmeessä lukemassa; Feserin kirjoitukset ovat totuttuun tapaan erittäin hyviä. (Suosittelen myös Alvin Plantingan arviota Mind and Cosmos -teoksesta sekä Bill Vallicellan lukemisen arvoisia postauksia Nagelista.)

  

Tässä muutama korostamisen arvoinen pointti Feserin Nagel-kirjoituksista.

   

(1) Feser huomioi aivan oikein, että Nagelin kirjan tarkoituksena ei ole perehtyä syvällisesti anti-materialistisiin argumentteihin, vaan pikemminkin tutkia vaihtoehtoja materialismille. Nagel on uransa aikana jo argumentoinut kattavasti materialismia vastaan (esim. ”What Is It Like to Be a Bat?”, ”The Psychophysical Nexus” ja The Last Word); Mind and Cosmos -teoksessa Nagel ainoastaan mainitsee nämä aikaisemmin kattavammin puolustamansa argumentit, jonka jälkeen hän alkaa pohtia vaihtoehtoja reduktiiviselle materialismille. Kun siis kirjoitin omassa arviossani, että Nagelin olisi pitänyt käsitellä antimaterialistisia argumentteja kattavammin, en ehkä ollut aivan reilu. Tämä ei ole kirjan päätarkoitus. (Tosin pitäydyn siinä, että ”Why the Materialist Neo-darwinian Conception of Nature is Almost Certainly False” -alaotsikko on nimenomaan tämän vuoksi hieman harhaanjohtava.)

    

(2) Sekä Lieter ja Weisberg että Sober antavat Nagelille seuraavanlaisen vastalauseen. Mistä tiedämme, ettei tietoisuus ja järjellisyys voisi ilmestyä täysin materialistisen evoluutioprosessin tuloksena? Tämä voi kenties olla epätodennäköistä, mutta epätodennäköisiä asioita tapahtuu koko ajan. Tämänkaltainen ”vastalause” on kuitenkin todella heikko ja se yksinkertaisesti sivuuttaa Nagelin pääargumentin. Nagelin koko pointti on, että tietoisuuden ja materian välillä on kvalitatiivinen (ei vain kvantitatiivinen) ero, jonka vuoksi ensimmäinen reduktio jälkimmäiseen on mahdotonta, ei ainoastaan ”epätodennäköistä”.

  

Eräs pääperusteista antireduktionismille on seuraava. Moderni materialismi olettaa (ainakin implisiittisesti) Descartesilta, Galileolta ja muilta moderneilta ajattelijoilta perityn mekanistis-objektiivisen ainekäsityksen. Aine on tämän käsityksen mukaan objektiivisesti tarkasteltavissa olevaa sekä matemaattisesti kvantifioitavaa. Kaikki ilmiöt, jotka eivät mahdu tähän objektiiviseen materiaan, lakaistaan subjektiivisten mielien alaisuuteen. Lämpo, maku, haju ja muut kokemukselliset sekundaariset kvaliteetit eivät siis ole objektiivisessa aineellisessa maailmassa sinänsä, vaan subjektiivisissa mielissä, jotka kokevat tätä maailmaa. Mutta jos materia määritellään tällä tavalla objektiivisesti, niin tietoisuus – joka on essentiaalisesti subjektiivista – ei voi mitenkään olla mitään aineellista. Feser selittää tämän pointin niin selkeästi, että häntä kannattaa lainata pitkälti:

  

Take a stock example of reductive scientific explanation like the reduction of sound to compression waves, color to surface reflectance properties, or heat and cold to molecular motion.  The way these explanations work is by treating the appearance that sound, color, heat and cold present to us in conscious experience as mere appearance, as a projection of the mind that corresponds to nothing in objective, mind-independent reality.  What common sense understands by color, sound, heat and cold — the way red looks, the way a musical note sounds, the way a hot stove feels, and so forth — is held to have no objective reality, any more than the redness a person unknowingly wearing red-tinted contact lenses thinks he sees in all the objects around him really exists in those objects.  Instead, color is for scientific purposes essentially redefined by the method in terms of the surface reflectance properties that cause in us the subjective appearance of color; sound redefined in terms of the compression waves that cause in us the subjective appearance of sound; and heat and cold redefined in terms of the molecular motion that causes in us the subjective appearance of heat and cold.

Thus, as common sense understands color, sound, heat and cold, etc., the reductive method ends up treating the world as essentially colorless, soundless, devoid of temperature, etc.  What the method calls ”color,” ”sound,” ”heat” and ”cold” is in fact something different from what the man on the street thinks of when he hears these terms.  The ”red” that the method says exists in the material world is just the tendency of an object to absorb certain wavelengths of light and to reflect others.  The ”red” that the man on the street thinks exists in the object does not really exist in the object itself at all but only in his perceptual experience of the object.  The ”heat” that the method says really exists in the material world is just the motion of molecules.  The ”heat” that the man on the street thinks exists in the object does not really exist in the object at all but only in his perceptual experience of the object.  And so forth.

Now, Nagel’s point is not that there is something wrong per se with overthrowing common sense in this way.  It is rather that whatever value this method has, it cannot coherently be applied to the explanation of conscious experience itself.  If the reductive method involves ignoring the appearances of a thing and redefining the thing in terms of something other than the appearances, then since our conscious experience of the world just is the way the world appears to us, to ignore the appearances is in this case just to ignore the very phenomenon to be explained rather than to explain it.  Consciousness is for this reason necessarily and uniquely resistant to explanation via the same method scientific reductionism applies to everything else.  For the application of the method in this case, writes Nagel, ”does not take us nearer to the real nature of the phenomenon: it takes us farther away from it.”  To treat the appearances as essentially ”subjective” or mind-dependent is precisely to make them incapable of explanation in entirely ”objective” or mind-independent terms.

Hence ”in a sense,” Nagel continues, ”the seeds of this objection to the reducibility of experience are already detectable in successful cases of reduction.”  As I have put it myself in several places, the reductive method in question is like the method of getting rid of all the dirt in the house by sweeping it under a certain rug.  While this is a very effective way of getting rid of the dirt everywhere else, it is not a strategy that could possibly be used to get rid of the dirt under the rug itself.  On the contrary, it only makes the problem of getting rid of that dirt even worse.  And that is exactly why the mind-body problem as it is understood today essentially came into existence with Galileo, Descartes, and Co. and has remained unsolved to the present day.  What these early modern thinkers wanted (for certain practical and political ends) was a completely quantitative, mathematical description of the world.  Irreducibly qualitative features — secondary qualities, final causes, and the like — since they would not fit this model, were thus essentially defined away as mere projections, ”swept under the rug” of the mind as it were.  But that only makes the idea of dealing with the mind itself in the same manner even more hopeless.  For these early moderns, the mind just is, you might say, the holding tank for everything that doesn’t fit their quantitative method.  Naturally, then, that method cannot coherently be applied to the mind itself.

Now the lesson Nagel drew from this in the 1974 article was not that physicalism is false so much as that ”physicalism is a position we cannot understand because we do not at present have any conception of how it might be true.”  But the early moderns who inaugurated this conceptual revolution tended to draw the stronger conclusion.  Indeed, writers like Cudworth and Malebranche saw that the method in question can be used to argue for a kind of mind-body dualism.  For if you maintain that color, sound, heat, cold, odor, taste, etc., as common sense understands these features, do not exist in matter, then they do not exist in the brain or body any more than they exist in the material world external to the brain and body.  If they do exist in the mind, though, then the mind must not be material.  Dualism can hardly be refuted by the reductive method, then, precisely because dualism follows from that method . . .

What you cannot coherently be, consistent with the reductive method described, is any sort of reductive materialist, which has been at least historically the standard form of materialism.  And this, I would say, is why materialism was so rare in modern philosophy before the late twentieth century.  It takes real historical ignorance seriously to think that the scientific revolution somehow supports reductive materialism and that Descartes, Locke, Berkeley, et al. were non-materialists merely because they didn’t have the courage and/or foresight to follow out the implications of that revolution.  In fact, they were the ones who were consistently following out those implications, while materialists like Hobbes were the wishful thinkers.  Perhaps the proud ignorance of the history of philosophy that some (though by no means all) of the early analytic philosophers exhibited made it possible for materialism widely to come to seem plausible by the 1960s.  (To paraphrase Newman, to be deep in the history of philosophy is to cease to be a naturalist.  That’s certainly what led me away from naturalism, anyway.) (Feser, ”Nagel and his critics, part II”)

   

Kannattaa muistaa tästä turhan pitkästä lainauksesta ainakin seuraavat sanat: harhaluulo, jonka mukaan tieteellinen vallankumous jollakin tapaa tukisi reduktiivista materialismia, vaatii kovan luokan tietämättömyyttä tieteen ja filosofian historiasta.

    

(3) Lopuksi on hyvä painottaa vielä kerran Nagelin kiriitkin kohdella, Duprén epäreilun NDPR-arvion valossa. Dupré antaa ymmärtää, että Nageli kritisoisi uus-darwinistista evoluutioteoriaa sinänsä, vaikka tosiassa Nagelin kritiikin kohde on metafyysinen materialismi, jonka mukaan voimme selittää jokaisen inhimillisen aspektin fysiikan, kemian ja biologian keinoin. Feser vastaa Duprélle näin:

  

The unwary reader might conclude from this that Nagel is claiming that neo-Darwinian evolutionary theory is in general wrong, that he thinks he can show this on the basis of a few problem cases, and that he doesn’t think he needs to bother with empirical evidence of the sort Dupré cites in order to show it.  But that is a grave distortion of Nagel’s position.  In fact Nagel does not say that neo-Darwinian explanations are in general wrong; he merely thinks that that sort of explanation cannot account for every single aspect of the biological realm.  And when Nagel criticizes neo-Darwinians for their metaphysical commitments, he is not saying that Darwinian explanations in general lack grounding in empirical evidence; rather, he is claiming that the view that neo-Darwinism can account for every single aspect of the biological realm is based in metaphysics rather than science — specifically, in a materialist metaphysics.

Indeed, it is this conjunction of neo-Darwinism with materialism that is the target of Nagel’s attack in the book — not neo-Darwinian evolutionary theory per se and certainly not evolution more generally.  Nagel does not want to abandon evolutionary explanations, and he does not deny that many such explanations have empirical evidence in their favor.  Rather, he wants to situate evolutionary theory within a different, non-materialist metaphysics. (”Nagel and his critics, part V”)

  

Mutta niinkuin totesin, käykää toki lukemassa Feserin, kuten myös Plantingan ja Vallicellan, Nagel-kirjoituksia itse.