Prolegomena 7 (1) 2008: 37–59 Mary's Scientific Knowledge* LUCA MALATESTI University of Hull – Philosophy, Hull HU6 7RX United Kingdom l.malatesti@hull.ac.uk ORIGINAL SCIENTIFIC ARTICLE / RECEIVED: 26–01–2007 ACCEPTED: 14–10–2007 aBstract:.Frank.Jackson's.knowledge.argument.(KA).aims.to.prove,.by.means.of. a.thought.experiment.concerning.the.hypothetical.scientist.Mary,.that.conscious. experiences.have.non-physical.properties,.called.qualia .Mary.has.complete.scientific.knowledge.of.colours.and.colour.vision.without.having.had.any.colour. experience .The.central.intuition.in.the.KA.is.that,.by.seeing.colours,.Mary.will. learn.what it is like.to.have.colour.experiences .Therefore,.her.scientific.knowledge.is.incomplete,.and.conscious.experiences.have.qualia .In.this.paper.I.consider.an.objection.to.the.KA.raised.by.Daniel.Dennett .He.maintains.that.the.KA. is.vitiated.by.Jackson's.account.of.Mary's.scientific.knowledge .While.endorsing. this.criticism,.I.will.defend.the.plausibility.and.relevance.of.the.type.of.strategy. involved.in.the.KA.by.offering.an.account.of.Mary's.scientific.knowledge .This. account.involves.formulating.a.reasonable.and.not.immediately.false.version.of. the.physicalist.thesis.with.regard.to.colour.experiences .Whether.this.version.of. the.KA.is.successful.against.this.type.of.physicalism.is.not.investigated.here keywords:.Conscious.experience,.experiences.of.colours,.knowledge.argument,. physicalism,.qualia 1. Introduction Frank.Jackson's.knowledge.argument.is.a.famous.objection.to.physicalism 1.The.most.discussed.version.of.this.argument.relies.on.a.thought.experiment.concerning.Mary,.a.vision.scientist.who.has.complete.scientific. knowledge.of.colours.and.colour.vision,.but.has.never.had.colour.experi- *.I.have.presented.versions.of.this.paper.in.research.seminars.at.the.University.of.Siena.(Italy).and.the.University.of.Rijeka.(Croatia) .I.would.like.to.thank.the.participants.for. their.objections.and.suggestions .In.addition,.I.am.very.grateful.to.the.anonymous.referee. of.this.journal.for.criticisms.that.prompted.substantial.revisions 1.Jackson.(1982).and.Jackson.(1986) .However,.Jackson.has.since.renounced.this;.see. Jackson.(1998).and.Jackson.(2004) . 38 Prolegomena 7 (1) 2008 ences .In.fact,.Mary.has.been.held.captive.in.a.monochromatic.environment,.where.she.acquired.her.scientific.knowledge.only.by.seeing.white,. black.and.shades.of.grey .According.to.Jackson,.when.Mary.is.released. from.this.environment.and.sees.coloured.objects,.she.acquires.new.knowledge.that.is.not.to.be.found.among.her.complete.scientific.knowledge .He. concludes. that. there.are. facts.concerning.colour.experiences. that.scientific.knowledge.can.neither.describe.nor.explain .Specifically,.these.facts. involve.the.occurrence.of.certain.non-physical.properties.of.experiences. that.he.calls.qualia I.will.argue.that.Jackson's.knowledge.argument.requires.major.revision .In.fact,.Jackson.does.not.offer.a.precise.characterisation.of.Mary's. scientific.knowledge .As.Daniel.Dennett. has. shown,. this. lack.of.precision. authorises. legitimate. interpretations. under. which. his. reasoning. is. unintelligible .Moreover,. Jackson's.account.of.Mary's. scientific.knowledge.leaves.open.possibilities.that.could.undermine.the.soundness.of.the. knowledge.argument 2 Nevertheless,.I.will.argue.that.the.type.of.strategy.involved.in.Jackson's.argument.might.still.be.viable .The.central.problem.to.be.addressed. here.is.that.of.striking.the.right.balance.between.the.intelligibility.of.what. Mary.knows.before.her.release.and.the.strength.of.the.knowledge.argument's.conclusion .Jackson's.argument,.which.is.aimed.at.a.highly.abstract. version.of.physicalism,. is. intended. to. show. that. there. are.non-physical. facts.and.properties This.paper.offers.a.version.of. the.knowledge.argument. that.constitutes. a. substantive,. interesting. challenge. to. contemporary. accounts. of. conscious.colour.experience .This.version.is.directed.against.a."modest",. well-defined,.and.reasonable.formulation.of.an.idea.shared.by.many.physicalists,.namely,.that.science.can.accommodate.colour.experiences .While. articulating.and.defending.this.formulation.of.the.knowledge.argument,.I. will.not.evaluate.the.soundness.of.such.reasoning 2. Knowledge Beyond Our Understanding The.knowledge.argument.can.be.formulated.as.follows: (1). .Mary,.before.her.release,.has.complete.scientific.knowledge.of. the.facts.concerning.colours.and.colour.vision,.without.having. had.any.conscious.experiences.of.colours (2). .By.seeing.a.coloured.object.after.her.release,.Mary.acquires.new. knowledge about.colour.experiences 2.Dennett.(1991:.399–403) 39L. MALATESTI: Mary's Scientific Knowledge Therefore: (3).There.are.facts.that.are.not.physical Let.us.consider.the.two.premises.of.the.argument .The.second.concerns.knowledge.that.Mary.allegedly.acquires.by.having.chromatic.colour. experiences .Jackson.claims.that.this.knowledge.involves.the.occurrence. of.qualia .By.the.term.qualia.he.wishes.to.refer.to."certain.features.of.the. bodily.sensations.especially,.but.also.of.certain.perceptual.experiences". (Jackson,.1982:.469) .According.to.Jackson,.this.suggests.that,.by.seeing. coloured.objects,.Mary.comes.to.know.facts.about.her.colour.experiences. that. involve. the. occurrence.of. non-physical.qualia . For. instance,. when. Mary.sees.a.red.object,.she.will.learn.that.her.experience.of.a.red.object. has.a.certain.feature .This.feature.is.a.quale.that.she.did.not.know.about. before.her.release .I.will.refer.to.such.knowledge.as.knowledge of what it is like.to have a colour experience .Many.have.focused.critical.attention. on.this.second.premise.of.the.knowledge.argument 3.However,.the.other. premise.likewise.requires.careful.scrutiny The.first.premise.of.the.knowledge.argument.involves.a.characterisation.of.Mary's.scientific.knowledge .This.scientific.knowledge.should. comprise. the. kinds. of. facts. that,. according. to. the. physicalist,. exhaust. all. there. is. to.know.about.colour.experience .Jackson.maintains. that.he. does.not.need.a.precise.characterisation.of.physical.facts.or,.in.his.words,. "'physical. information'. and. the. correlative. notion. of. physical. property,. process,.and.so.on" 4.Instead,.he.assumes.that.it.is.enough.for.his.purposes. to.say.of.Mary.that."[s]he.knows.all.the.physical.facts.about.us.and.our. environment,.in.a.wide.sense.of.'physical'.which.includes.everything.in. completed.physics,.chemistry.and.neurophysiology".(Jackson.1986:.567) . Additionally,.he.claims.that.Mary.knows.facts.concerning.the."functional. roles".played.by.states.of. the.nervous.system 5.This.characterisation. is,. however,.not.satisfactory In. the.knowledge.argument,. the.assumption. that.Mary,.by.seeing.a. coloured.object,.comes.to.know.something.that.she.did.not.know.before. her.release.plays.a.central.role .The.alleged.novelty.of.this.knowledge.and,. supposedly,.our.understanding.of.its.nature.should.stem.from.the.contrast. with.what.she.knew.before.her.release .However,.as.Daniel.Dennett.has. persuasively.pointed.out,.we.cannot.contrast.Mary's.scientific.knowledge. with.her.knowledge.of.what.it.is.like.to.have.a.colour.experience 6.In.fact,. grasping.her.scientific.knowledge.is.a.task."so.preposterously.immense,. 3.For.an.overview.of.this.debate,.see.Nida-Rümelin.(2002) 4.Jackson.(1982:.469) 5.Jackson.(1986:.567) 6.A.similar.observation.is.offered.by.Churchland.(1986) 40 Prolegomena 7 (1) 2008 you.can't.even.try .The.crucial.premise.is. that.'She.has.all. the.physical. information '. That's. not. readily. imaginable. [...]". (Dennett. 1991:. 399) . Moreover,.the.inadequate.characterisation.of.Mary's.scientific.knowledge. allows.Dennett.to.offer.a.thought.experiment.to.counter.Jackson's.argument Dennett.assumes.that.if,.before.her.release,.Mary.lacked.knowledge. of.certain.features.of.colour.experiences,.then.upon.her.release.she.will.be. unable,.when.looking.at.a.blue.banana,.to.recognise.that.it.has.the.wrong. colour .He.then.tells.the.following.story: And.so.one.day,.Mary's.captors.decided.it.was.time.for.her.to.see.colors .As. a.trick.they.prepared.a.bright.blue.banana.to.present.as.her.first.color.experience.ever .Mary.took.one.look.at.it.and.said.'Hey!.You.tried.to.trick.me!.Bananas.are.yellow,.but.this.one.is.blue!'.Her.captors.were.dumbfounded .How. did.she.do.it?.'Simple,'.she.replied .'You.have.to.remember.that.I.know.everything.–.absolutely.everything.–.that.could.ever.be.known.about.the.causes. and.effects.of.color.vision .So.of.course.before.you.brought.the.banana.in,.I. had.already.written.down,.in.exquisite.detail,.exactly.what.physical.impression.a.yellow.object.or.a.blue.object.[...].would.make.on.my.nervous.system . So.I.already.knew.exactly.what.thoughts.I.would.have.(because,.after.all,.the. "mere.disposition".to.think.about.this.or.that.is.not.one.of.your.famous.qualia,.is.it?) .I.was.not.in.the.slightest.surprised.by.my.experience.of.blue.[...]. I.realize.that.it.is.hard.for.you.to.imagine.that.I.could.know.so.much.about. my.reactive.dispositions.that.the.way.blue.affected.me.came.as.no.surprise . Of.course.it's.hard.for.you.to.imagine .It's.hard.for.anyone.to.imagine.the. consequences.of.someone.knowing.absolutely.everything.about.anything!'. (Dennett.1991:.399–400) Some.have.maintained.that.Dennett.uses.this.story.to.deny.that.Mary. learns.anything.upon.her.release 7.However,.his.aim.here.appears. to.be. more.modest:."My.point.is.not.that.my.way.of.telling.the.rest.of.the.story. proves.that.Mary.doesn't.learn.anything,.but.that.the.usual.way.of.imagining.the.story.does.not.prove.that.she.does .It.doesn't.prove.anything.[...]". (Dennett.1991:.400) .Thus.Dennett. is.not.arguing. that.Mary,.by. seeing. coloured.objects,.does.not.undergo.an.epistemic.progress .Rather,.he.tries. to.disqualify.the.intuition.supporting.the.conclusion.that.she.might.learn. something .There.are.also.good.reasons.for.thinking.that.this.is.the.only. conclusion.we.can.draw.from.Dennett's.story Dennett.wants.us.to.imagine.a.situation.in.which.Mary.does.not.learn. anything.new.by.having.conscious.experiences .He.suggests.that.Mary's. 7.See.Alter. (1999). and.Chalmers. (1996:.145) .This. reading. is. probably. suggested. by. the. fact. that.Dennett.has. argued. in.other.places. for. eliminating.qualia;. see.Dennett. (1988) 41L. MALATESTI: Mary's Scientific Knowledge complete. knowledge. might. consist. of. laws. stating. causal. correlations. between.types.of.experiences.and.types.of.thoughts .In.particular,.Mary. knows.that.if.a.subject.is.presented.with.a.blue.banana,.she.will.have.a. thought.expressible.as:."This.is.blue" .Thus,.by.seeing.the.blue.banana,. Mary.comes.to.know.that.people.who.have.this.kind.of.experience.think:. "This.is.blue" .Therefore,.we.can.have.intuitions.about.Mary's.case.that. do.not.support.the.knowledge.argument .However,.does.Dennett's.story. add. anything. to. the. observation. that. we. cannot. grasp. Mary's. scientific. knowledge? It. appears. that.Dennett's. account.of.Mary's.case.exploits. the. same. lack. of. understanding. of. her. scientific. knowledge. which. he. denounces. in.Jackson's.knowledge.argument .Indeed,.let.us.assume,.for.the.sake.of. argument,. that. there.can.be.scientific. laws.connecting.scientifically.described.experiences.with.thoughts 8.Also,.although.Dennett.does.not.explain.how.this.is.possible,.we.can.concede.that.Mary's.ability.to.recognise. the.colour.of.the.object.she.sees.enables.her.to.know.what.it.is.like.to.have. a.certain.colour experience Nevertheless,.in.order.to.judge.whether.Mary.passes.the.blue.banana. test,.we.need.a.more. substantial.understanding.of.her. scientific.knowledge .A.central.assumption.in.Dennett's.story.is.that.Mary,.by.just.looking. at.the.banana,.is.able.to.apply.the.law.correlating.the.conscious.experience. she.is.having.with.the.thoughts.usually.caused.by.this.type.of.experience 9. As.Dennett.puts.it:."Mary.took.one.look.at.it.and.said.'Hey!.You.tried.to. trick.me!'" .This.requires.that.Mary.can.recognise.the.colour.experience. involved.in.seeing.the.blue.banana.as.a.certain."physical.impression".on. her.nervous.system .However,.how.does.she.acquire.such.recognitional. capacity?.It.seems.that.we.are.not.in.a.position.to.say .On.the.other.hand,.it. could.be.maintained.that.a.relevant.factor.in.our.conclusion.that.Mary.was. not.fooled.might.lie.in.on.our.understanding.of.her.notion.of."physical.impression" .This.decision.cannot,.however,.be.based.on.Dennett's.sketchy. model.of.Mary's. scientific.knowledge . It. seems. that.a.more.substantial. account.of.her.scientific.knowledge.is.needed To.sum.up,.it.appears.that.Dennett's.response.makes.two.legitimate. demands.on.supporters.of.the.knowledge.argument .First,.they.should.provide.an.intelligible.account.of.what.Mary.knows.before.seeing.colours . Secondly,.they.have.to.prove.that.Mary.cannot.acquire.the.recognitional. capacities. involved. in. Dennett's. story. just. by. possessing. this. scientific. 8.Some.have.argued.that.thoughts.cannot.enter.into.any.nomological.correlation;.see,. for.example,.the.very.influential.Davidson.(1970) 9.Howard.Robinson.shows.clearly.how.this.assumption.is.implicit.in.Dennett's.story. (Robinson,.1993:.175) 42 Prolegomena 7 (1) 2008 knowledge .In.the.following.sections,.I.will.argue.that.these.two.demands. can.be.satisfied 3. Defining the Physical Our. task. is. to. offer. an. intelligible. characterisation. of. Mary's. scientific. knowledge .In.addressing.this.challenge,.we.can.begin.with.the.plausible. assumption. that. the.knowledge.argument.attacks.a.version.of.physicalism.which.has.a.theory-based conception.of.being.physical .According.to. this.conception,.a.certain.entity.is.physical.when.a.certain.physical.theory. includes.expressions.that.can.refer.to.it .In.fact,.the.knowledge.argument. requires.that.Mary.knows.completed.physics,.chemistry.and.neuroscience,. and.that.if.a.fact.escapes.this.knowledge,.then.it.is.non-physical A. version. of. physicalism. with. a. theory-based. conception. of. being. physical.faces.a.dilemma 10.On.the.first.horn.of.this.dilemma,.if.we.define. "being.physical".by.referring.to.some.ideally.complete.future.(or.possible).physical.theory,.the.notion.of."physical".appears.to.lack.content .In. fact,.we.cannot.predict.what.entities.or.laws.an.ideally.complete.future.(or. possible).physics.might.refer.to On.the.second.horn.of.the.dilemma,.if.the.definition.of."physical".is. based.on.current.physical.theory,.then.physicalism.is.false .In.fact,.if.the. physical. is.defined.as.whatever.is.described.by.current.microphysics.or. other.contemporary.scientific.doctrines,.then.new.particles.discovered.by. science.in.the.future.will.not.be.physical,.and.thus.the.physicalist.claim. that.everything.is.physical.would.be.false .As.seen.in. the.previous.section,.Jackson's.claim.that.Mary.knows.all.the.physical.facts.in.completed. physics. and. other. sciences. appears. to. expose. his. reasoning. to. the. first. horn.of.the.dilemma 11.On.the.other.hand,.if.Mary's.scientific.knowledge. is.grounded.in.contemporary.physics,.the.knowledge.argument.would.be. a.redundant.objection.to.a.false.doctrine A.supporter.of. the.knowledge.argument.might.avoid.these.difficulties.by.offering.an.account.of."being.physical".which.is.alternative.to.the. theory-based.account .For.example,.by.endorsing.an.object-based.conception.of.the.physical,.physical.entities.might.be.defined.as.those.of.the.same. type.as.some.entity.taken.to.be.paradigmatically.physical 12.The.central. idea.in.this.account.is.that.paradigmatically.physical.entities.can.be.intro10.On.this.problem.with.physicalism,.see.Hempel.(1980),.Crane.and.Mellor.(1990). and.Montero.(1999) 11.This. reading. is. supported. by. Dennett. (1991:. 399–403). and. Churchland. (1986:. 331–334) .See.also.Mellor.(1993) 12.See.Jackson.(1998:.6–7) 43L. MALATESTI: Mary's Scientific Knowledge duced.without.any.reference.to.contemporary,.future.or.possible.science . Non-sentient.ordinary.objects.such.as. tables.and.chairs.can.be. taken.as. paradigmatically.physical .Thus.we.might.define.physical.properties.and. relations.as.those.which.are.required.in.order.to.describe.paradigmatically. physical.entities This.object-based.conception.of. the.physical.has. its.problems .The. possibility.of.panpsychism. threatens. this.account.of."being.physical" 13. Panpsychists.believe.that.every.entity.has.a.mind .On.this.view,.the.paradigmatically.physical.objects.referred.to.in.the.object-based.account.of.the. physical.have.a.mind .Nevertheless,.the.object-based.account.requires.the. existence.of.non-sentient.objects,.and.so.proponents.of.this.view.must.exclude.the.possibility.of.panpsychism .However,.their.theory.does.not.seem. to.have.the.resources.to.specify.further.the.nature.of.these.non-sentient.objects .It.appears.that.they.merely.exclude.the.possibility.of.panpsychism.by. definition .However,.although.panpsychism.may.strike.us.as.completely. implausible,.the.possibility.of.it.cannot.be.ruled.out.by.stipulation.alone .It. seems.we.need.some.substantive.account.of.the.nature.of.ordinary.objects. in.order.to.rule.out.that.they.have.a.mind The.difficulty.created.by.the.possibility.of.panpsychism.is.an.instance. of.a.deeper.problem.with.the.object-based.account .This.account.of. the. physical. relies.on. the. idea. that.we.can.have.an.ordinary.understanding. of.what.type.of.properties.might.figure.in.a.complete.account.of.objects. such.as.chairs.and.tables .However,.our.ordinary.understanding.of.these. properties.might. turn.out. to.be. inadequate . It. is.enough.to.consider. the. image.of. reality.provided.by.contemporary.physics .The.ultimate.particles,.properties.and.laws.that.this.science.invokes.in.providing.an.account. of.ordinary.objects.are.very.different.from.those.we.can.contemplate.in. ordinary.experience 14.Thus.a.version.of.physicalism.with.an.object-based. account.can.even.contradict.physics,.and.endorsing.such.a.theory.requires. facing.the.possibility.that.many.of.the.basic.assumptions.of.contemporary. physics.are.false .Not.many.physicalists.would.be.willing.to.develop.an. account.of.physical.reality.alternative.to.the.one.that.contemporary.physics.provides The.problems.afflicting. the. theory-based.and.object-based.conceptions. of. being. physical. might. be. avoided. by. denying. one. assumption. that.they.share,.namely,.the.idea.that.formulating.physicalism.requires.a. characterisation.of.physical.entities 15.Joseph.Levine,.for.example,.has.recently.argued.that.physical.properties.should.be.defined.per via negativa. 13.Jackson.(1998:.7) 14.A.criticism.of.this.type.can.be.found.in.Levine.(2001:.20) 15.This.account.is.offered.in.Montero.(1999) .See.also.Levine.(2001:.20–21) 44 Prolegomena 7 (1) 2008 in.philosophical.discussions.of.the.mind-body.problem .He.contends.that. we.have.a.clear.enough.grasp.of.mental.properties .In.particular,.the.mental. is. characterised.by.phenomenal properties, which.specify.what. it. is. like.to.have.mental.states,.and.representational.properties,.which.define. the.content.of.mental.states .Thus.he.suggests.that.physicalism.(or,.in.his. words,."materialism").should.be.understood.as.the.thesis.that.non-mental. properties.have.ontological.and.explanatory.priority.over.mental.ones 16 This.characterisation.of.the.physical.per via negativa.should.be.rejected .In.fact,.it.undermines.one.very.good.reason.for.endorsing.physicalism .Physicalists.place.confidence.in.the.explanatory.power.of.scientific. knowledge,.by.virtue.of.current.developments.in.contemporary.science . In.particular,.many.physicalists.have.been. impressed.by.results. in.biology.and.neuroscience.that.have.explained.many.aspects.of.both.normal. and.pathological.human.behaviour 17.Thus.it.is.central.to.the.physicalist. project.to.offer.a.conception.of.the.mind.that.is.not.only.consistent.with. contemporary.science,.but.could.also.aid.scientific.progress 18 Clearly,.justifying.physicalism.by.referring.to.current.scientific.practice.must.involve.a.theory-based.conception.of.the.physical .However,.this. leads.us.back.to.the.dilemma.considered.above .Therefore,.we.must.see. whether.we.can.formulate.an.intelligible.version.of.the.knowledge.argument.without.abandoning.a.theory-based.conception.of.being.physical An.intelligible.and.not. immediately.false.version.of.physicalism.in. the.philosophy.of.mind.can.be. tied. to.contemporary.physics,19.without. endorsing.the.strong.yet.implausible.claim.that.our.contemporary.physical.knowledge.provides.the.ultimate.catalogue.of.physical.entities .This. "modest".formulation.of.physicalism.relies.on.two.assumptions .The.first. is.that.the.current.physics.of."ordinary.matter".is.complete .The.second. is.that.the.scientific.study.of.the.mind.can.be.appropriately.related.to.the. contemporary.scientific.study.of.ordinary.matter .Let.us.clarify.these.two. claims The.first.assumption.of.this."modest.formulation".of.physicalism.implies.that.a.class.of.macroscopic.phenomena.can.be.completely.described. and.explained.in.terms.of.the.principles.and.properties.of.current.physics . 16.Levine.(2001:.21) 17.David.Papineau.illustrates.how.the. idea.of. the.completeness.of.physics. is.not.a. methodological.or.metaphysical.principle.based.on.a priori.considerations .He.argues.that. advancements. in. the.understanding.of.neurophysiology.due. to.biochemistry. in. the. first. half.of. twentieth.century.are.central. to.establishing. this.principle .See.Papineau. (2002:. 232–256) 18.See.Fodor.(1974),.Smart.(1959).and.Churchland.(1986) 19.A.proposal.of.this.type.is.forcefully.presented.in.Smart.(1978).and.Smart.(1989) . 45L. MALATESTI: Mary's Scientific Knowledge Jack.Smart.illustrates.this.by.referring.to.the.position.of.the.physicist.Gerald.Feinberg:20 [T]he.theory.of.the.electron,.proton,.neutron,.neutrino.and.photon.and.their. anti-particles,.when.they.have.such,.is.enough.to.explain.the.properties.of. ordinary.matter.(not.what.goes.on.inside.neutron.stars.or.inside.black.holes,. or.the.behaviour.of.the.transitory.particles.created.only.with.big.cyclotrons) . Feinberg.thus.holds.that.the."Thales.Problem".(of.what.the.world.of.familiar. objects.is.made.of).has.essentially.been.solved .(Smart.1989:.81) Thus.we.should.endorse.Smart's.claim.that.changes.in.theories.concerning.phenomena.at.the.sub-atomic.level,.which.are.studied.under.special. laboratory.conditions,.can.be.expected .Moreover,.we.can.expect.transformations.in.those.theories.that.consider.the.universe.as.a.whole .However,. similar.changes.will.not.affect.scientific.descriptions.and.explanations.of. macroscopic.phenomena.involving.ordinary.matter .There.will.be.no.discoveries.altering.the.fact.that.the.hydrogen.atom.contains.one.proton.and. one.electron,.or.that.water.is.H2O The.second.assumption.of.the."modest".formulation.of.physicalism. establishes.a.programme.for.unifying.the.science.of.the.mind.with.that.of. ordinary.matter .Physicalists.have.notoriously.disagreed.on.the.proper.formulation.of.this.programme .Some.articulate.it.in.reductive.terms;.specifically,.they.assume.that.psychology.will.be.reduced.to.neuroscience,.given. that,.in.general,.each.type.of.mental.state.is.identical.to.a.certain.type.of. brain.state 21.Other.physicalists.or.naturalists.combine.the.thesis.of.the.ontological.primacy.of.the.physical.over.the.mental.with.some.notion.of.the. autonomy.of.psychology.from.neuroscience.and.physics 22.Thus,.instead. of.endorsing.reductionism,.they.claim.that.each.token.of.a.type.of.mental. state. is. identical. to. a. certain.physical. token .Moreover,. they. argue. that. relations.of.supervenience.or.emergence.which.are.weaker.than.identity. exist.between.types.of.mental.states.and.certain.types.of.physical.states . Insofar.as.we.assume.that.Mary.knows.the.relevant.scientific.disciplines. involved.in.the.physicalist.unification.programme,.we.need.not.decide.on. this.issue The."modest".formulation.of.physicalism.appears. to.be.a.plausible. and.intelligible.general.version.of.physicalism.in.the.philosophy.of.mind . However,.as.it.stands,.it.does.not.offer.a.precise.enough.characterisation. of.Mary's.scientific.knowledge .Clearly,.Dennett's.concerns.cannot.be.addressed.by.assuming.that.Mary.knows.about.the.properties.of.conscious. 20.Feinberg.(1966) 21.Smart.(1959).and.Hill.(1991) 22.Fodor.(1974).and.Putnam.(1967) .Dretske.(1995).offers.a.non-reductive.naturalistic.account.of.colour.experience 46 Prolegomena 7 (1) 2008 experiences.investigated.by.unspecified.psychological.doctrines .Moreover,.claiming.that.these.doctrines.are.to.be.unified.with.the.study.of.the. macroscopic.physical.properties.of.the.brain.leaves.huge.gaps.in.our.understanding.of.her.knowledge .We.need,.then,.to.examine.whether.a.more. detailed.characterisation.of.Mary's.scientific.knowledge.can.be.provided. within.the.general.framework.of.modest.physicalism 4. A Scientific Categorisation of Colour Experiences The.knowledge.argument. is.supposed. to.reveal. the.existence.of.qualia,. understood.as.non-physical.properties.that.typify.conscious.experiences . Therefore,.two.colour.experiences.are.said.to.be.of.the.same.type.if.they. share.the.same.quale .If.we.wish.to.formulate.the.knowledge.argument.as. a.challenge.to.modest.physicalism,.this.suggests.how.the.problem.of.accounting.for.Mary's.scientific.knowledge.might.be.addressed .The.idea.is. to.investigate.whether.we.can.ascribe.to.her.a.complete knowledge.of.the. contemporary.psychometric.methods.employed.in.describing.the.features. that.ground.the.categorisation.of.colour.experiences In. contemporary. science,. spatial models are. used. to. describe. how. we.categorise.different.types.of.stimuli .Here.we.are.interested.in.colour. spaces.that.describe.our.categorisation.of.colours 23.I.will.refer.to.a colour solid.as.one.such.colour.space .A.colour.solid.can.represent.the.ordering.of. colours.that.we.discriminate.by.means.of.three.dimensions:.hue,.saturation.and.lightness or.brightness (see.Figure.1) Figure 1.–.A colour solid 23.The. central. role.of. quality. spaces. in. contemporary. colour.vision. science. is. explored.in.detail.in.Clark.(1993).and.Clark.(2000) .See.also.Palmer.(1999a) 47L. MALATESTI: Mary's Scientific Knowledge Hue.is. the.dimension.we.normally.associate.with. the.basic.colours. of.surfaces .In.the.colour.solid,.hue.is.represented.by.the.angular.direction.in.the.horizontal.plane,.from.the.central.axis.of.the.solid.to.the.point. position.representing.that.colour .Saturation.is.the."vividness".of.a.colour . Chromatic.colours.of.the.same.hue.can.differ.in.strength.of.hue,.with.less. saturated.colours.closer. to.grey. than.more.saturated.ones . In. the.colour. solid,.the.saturation.of.a.certain.colour.is.represented.by.the.distance.of. the.point.representing.that.colour.from.the.colour.solid's.central.axis .The. third.dimension.of.colour.is.brightness,.i e .the.relative.lightness.or.darkness.of.a.particular.colour,.from.black.to.white 24.In.the.colour.solid,.the. brightness. of. a. certain. colour. is. represented. by. the. height. of. the. point. representing.that.colour .The.colour.solid.encodes.information.about.the. colours.that.subjects.discriminate .Points.in.this.space.are.taken.to.represent.shades.of.colour,.as.these.points.are.individuated.by.specific.values. in.the.axes.representing.hue,.saturation.and.lightness .In.addition,.the.relative.distances.of.points.representing.shades.of.colour.define.the.relative. similarities.between.those.shades .For.example,.orange.would.be.situated. between.red.and.yellow,.because.subjects.find.it.more.similar.to.these.two. colours.than,.say,.to.blue 25 Let. us. now. consider. how. colour. spaces. are. determined .There. are. experimental.psychophysical.procedures.for.determining.how.individuals. categorise. colours .These. consist. in. stimulating. subjects'. visual. system. and.registering.their.discriminatory.responses .The.stimuli.employed.are. lights,.which.are.characterised.physically.in.terms.of.the.wavelength.and. intensity.of.the.electromagnetic.waves.composing.them .Discriminatory. responses. are. observable. behaviours;. scientists. usually. examine. verbal. reports,.but.other.kinds.of.behavioural.clues.can.also.be.used .In.particular,.psychophysicists.use.a.notion.of.indiscriminability.that.satisfies.some. statistically.defined.conditions,.such.that.establishing.whether.two.stimuli. are.indiscriminable.requires.the.reiterated.presentation.of.pairs.of.stimuli. of. the. same. type .Thus,. if. different. individuals. with. normal. vision. fail. 24.Generally.the.term."brightness".is.used.to.indicate.a.feature.of.colours.seen.through. apertures.or.those.of.self-luminous.objects.like.the.sun.or.lamps .In.contrast,."lightness" refers.to.a.feature.of colours.of.objects.not.seen.through.apertures.or.perceived.as.selfluminous 25.The.colour.solid.also.encodes.information.about.relations.of.composition.between. colours .Certain.hues.can.be.analysed.in.terms.of.which.hues.are.more.basic .Orange,.for. instance,.appears.to.contain.both.redness.and.yellowness .For.this.reason,.a.certain.shade. of.orange.will.be.represented.by.a.location.between.red.and.yellow .In.contrast,.particular. shades.of.red,.green,.blue.and.yellow.do.not.appear.to.be.composed.of.any.colours .The. colour.solid.also.represents.relations.of.opponency.between.colours .For.example,.it.shows. that.there.are.no.hues.which.appear.reddish.and.greenish .In.fact,.there.is.no.point.in.the. colour.space.that.might.represent.such.hues 48 Prolegomena 7 (1) 2008 to.notice.any.difference.between.two.stimuli.in.a.statistically.significant. way,.the.two.stimuli.are.said.to.be.indiscriminable .These.procedures.determine.the.classes.of.indiscriminable.stimuli The.colour.solid.is.obtained.using.mathematical.procedures.applied. to.classes.of.indiscriminable.stimuli.determined.by.considering.subjects'. judgments. concerning. the. similarity. of. these. stimuli . These. methods. must.define.the.number.of.dimensions.of.the.colour.solid.and.the.structure.of.relations.of.similarity.between.its.points .Different.methods.have. been.investigated.to.this.end 26.A.family.of.statistical.procedures.known. as. multidimensional scaling (MDS). has. been. successfully. employed. in. psychophysics 27.We.can.illustrate.these.techniques.with.an.example .In. colour.science,.multidimensional.scaling.can.be.applied.to.similarity.matrices.representing.a.relation.of.similarity.among.stimuli .Table.1.shows. a. matrix. representing. similarity. ratings. of. monochromatic. light. stimuli. described.in.terms.of.their.wavelength 28.For.each.pair.of.stimuli,.a.numerical.value.represents.their.degree.of.similarity .These.values.have.been. determined.experimentally.mainly.by.registering.subjects'.discriminatory. judgements Wavelength 445 465 504 537 584 600 651 674 445 – 9 7 6 2 2 7 8 465 – 8 7 2 2 6 7 504 – 9 6 5 2 2 537 – 7 6 3 2 584 – 8 4 3 600 – 5 4 651 – 9 674 – Table 1.–.A similarity matrix for observers based on.Ekman.1954 26.Some.philosophers.have.investigated.these.procedures .Rudolf.Carnap,.for.instance,. in.his.attempt.to.provide.a.method.for.constituting.all.scientific.concepts.from.a.base.of. observational.primitives,.faced.the.problem.of.determining.colour.classes.originating.from. classes.of.pairs.of.certain.primitive.particulars;.Carnap.(1967:.107–136,.178–182) .Nelson. Goodman.subsequently.demonstrated.some.limitations.in.Carnap's.methods,.and.developed.an.alternative.approach;.see.Chapter.5.of.Goodman.(1977) .For.a.comparison.of.these. two.approaches,.see.Clark.(1993:.101–112) 27.The. use. of. MDS. for. determining. the. colour. space. was. advocated. by. Shepard. (1962) .An.introduction.to.MDS.is.offered.in.Clark.(1993:.210–221),.while.a.more.exhaustive.and.technical.presentation.can.be.found.in.Shifman.et.al .(1981) 28.Monochromatic.stimuli.are.those.characterised.by.a.single.wavelength 49L. MALATESTI: Mary's Scientific Knowledge Using.matrices.of.this.type,.a.spatial.model.is.determined.by.applying.the.algorithms.of.multidimensional.scaling 29.Figure.2.shows.a.map. obtained.by.applying.MDS.to.the.colour.similarity.data.in.Table.1 .The. MDS.procedure.shows.that. the.similarities.between.the.stimuli.concern. only.two.dimensions:.saturation.and.hue .This.is.because.the.initial.matrix.is.not.complete,.and.does.not.contain.enough.information.to.derive. the.dimension.of.brightness .In.principle,.however,.if.a.complete.matrix. of.similarity.is.available,.the.structure.and.dimensionality.of.a.complete. colour.space.are.obtainable.in.the.same.way Figure 2.–.Multidimensional scaling map based on the colour similarity data in Table 1 .(Coren,.Ward,.and.Enns.1999:.46) To.sum.up,.we.have.seen.that,.in.principle,.it.is.possible.to.use.classes. of.discriminatory.responses.to.light.stimuli.in.order.to.determine.the.dimensions.of.variations. involved. in.our.classification.of.colours . In.particular,.we.have.seen.that.each.colour.can.be.individuated.and.described. as.a.certain.position.in.a.colour.space .However,.we.still.need.to.specify. how.contemporary.science.can.describe.colour.experiences.by.means.of. colour.spaces 29.The.procedure.illustrated.here.is.an.instance.of.metric.multidimensional.scaling . In.fact,. the.matrix.under.consideration.presents.the.degree.of.similarity.between.the.responses.evoked.by.two.colour.stimuli. in.terms.of.a.specific.numerical.value .However,. it.is.also.possible.to.generate.a.colour.space.by.applying.non-metric.MDS.procedures .In. this.case,.the.matrix.does.not.contain.values.concerning.the.degree.of.similarity.between. stimuli .More.specifically,.it.is.possible.to.obtain.a.colour.space.by.applying.non-metric. MDS.to.matrices.representing.judgements.involving.the.triadic.relation."x is.more.similar. to.y than.z";.see.Clark.(1993:.220–221) 50 Prolegomena 7 (1) 2008 5. Accounting for Colour Experiences Colour.spaces.do.not.seem.to.advance.our.understanding.of.how.contemporary.science.aims.to.describe.the.features.that.ground.the.categorisation. of.colour.experiences .Thus.we.are.left.with.the.problem.of.providing.a. substantive.account.of.how.Mary.might.describe.such.experiences Surely,.any.commitment.to.a.theory.of.colour.should.be.avoided .In. fact,.views.on.the.relation.between.colours.and.colour.experiences.vary . Some. consider. colours. to. be. properties. of. experiences. or. other. mental. items,30.while.others.regard.colours.as.properties.whose.instantiation.in. an.object.is.identical.to.the.power.of.that.object.to.produce.a.colour.experience.of.a.certain.type 31.Finally,.some.consider.colours.to.be.objective. properties. of. external. objects 32. The. question. is. whether. colour. spaces. and.colour.experiences.can.be.correlated.in.a.way.that.is.relatively.neutral. with.regard.to.these.theories.of.colour Coloured.objects.appear.to.subjects.in.certain.ways .In.the.case.of.a. subject.seeing.a.red.patch,.this.patch.appears.to.her.to.have.certain.features;.in.particular,.it.looks.red.to.her .Now,.some.similarity.is.involved.in. seeing.an.object.of.a.certain.colour.and.an.object.that.merely.looks.like.it. has.that.colour .For.instance,.colour.illusions.may.be.caused.by.changes.in. illumination,.or.by.simultaneous.contrast .An.example.of.the.first.type.of. illusion.is.found.when.viewing.a.red.patch.under.yellow.light;.in.this.case,. the.patch.will.appear.visually.to.be.blue,.i e .it.seems.to.the.subject.to.have. the.same.colour.as.a.blue.patch .Likewise,.in.a.standard.demonstration.of. simultaneous.contrast,.a.grey.square.on.a.red.background.looks.greenish,. while.the.same.square.seen.against.a.green.background.looks.reddish 33.In. both.cases,.it.may.be.said.that.the.square.seems.to.have.the.same.colour. as.a.greenish.or.a.reddish.square,.respectively 34.Thus,.even.in.cases.of. illusory.perception,.objects.appear.to.have.a.certain.colour Colour.spaces.describe.the.colour.that.objects.seem.to.have .The.previous. section. showed. that. colour. spaces.are.determined.by.considering. discriminatory.responses.to.colour.stimuli .A.central.assumption.in.psychophysics.is.that.if.certain.individuals.cannot.discriminate.between.two. 30.Arguments.against.identifying.colours.with.physical.properties.of.the.stimuli.can. be.found.in.Hardin.(1988) 31.See.McGinn.(1991).and.Peacocke.(1984) 32.See.Byrne.and.Hilbert.(2003).and.Tye.(2000) . 33.See.Palmer.(1999b) 34.Assuming.that.there.is.such.a.similarity.does.not.involve.taking.a.position.on.the. nature.of.colour .I.am.not.speaking.of.whether.the.colour.of.an.object.is.the.colour.that. it.appears to have visually. in.certain.conditions . In.addition,.one.need.not.assume.that. colours.are.properties.of.colour.experiences 51L. MALATESTI: Mary's Scientific Knowledge stimuli,. then.these.stimuli.will.seem.to.them.to.have.the.same.colour 35. Moreover,.using.matrices.that.arrange.colour.stimuli.in.accordance.with. the.discriminatory.responses.they.elicit,.it.is.possible.to.determine.the.dimensions.involved .In.the.case.of.a.colour.solid,.for.example,.these.dimensions.are. saturation,.hue,. and.brightness .These.dimensions.are.derived. from.discriminatory. responses.assumed. to. reflect. relations.of.similarity. and.difference.in.the.ways.that.colours.appear.to.subjects .Therefore,.they. can.be.interpreted.as.dimensions.of.variation.in.colour .In.particular,.specific.values.for.these.dimensions.specify.a.location.in.the.colour.space,. which.can.be. regarded.as.a.description.of. the.colour.an.object.visually. appears.to.have 36 Besides.the.colours.objects.appear.to.have,.we.can.also.assume.that. there.are.qualitative properties.of.colour.experiences 37.Qualitative.properties.individuate.colour.experiences .Thus.if.two.colour.experiences.differ,. they.have.different.qualitative.properties .It.seems.that.we.can.establish.an. important.relationship.between.qualitative.properties.and.colours Some.authors.have.argued.that.colour.experiences.can.be.categorised. in.terms.of.their.typical.causes 38.A.colour.experience.is.of.a.certain.type. or,. in. our. terminology,. it. has. a. certain. qualitative. property,. if. a. certain. paradigmatic.object.would.produce.it.under.certain.conditions .For.example,.we.can.say.that.a.red-type.colour.experience.is.the.type.produced.by.a. certain.paradigmatically.red.thing.in.certain.suitable.circumstances It.has.also.been.suggested.that.when.something.appears.to.the.subject. to.be.a.certain.colour,.either.in.a.perceptual.case.or.in.an.illusory.one,.then. this. subject.has.a.certain. type.of.colour.experience .Thus.a.subject.can. have.a.colour.experience.that.is.not.produced.by.the.paradigmatic.object. involved.in.characterising.that.type.of.colour.experience .In.such.cases,. the.subject.is.said.to.be.having.this.type.of.colour.experience.because.the. stimulus. looks. like. the.paradigmatic.object .For.example,. if. the.subject. 35.More.precisely,.it.is.assumed.that.if.two.stimuli.are.globally indiscriminable (by. certain.individuals.in.certain.conditions),.then.they.appear.to.be.the.same.colour.(to.those. individuals.in.those.conditions) .A.certain.stimulus.x.is.globally.indiscriminable.from.stimulus.y,.if.and.only.if.for.any.stimulus.z,.x.is.indiscriminable.from.z.if.and.only.if.y.is.as.well . The.reasons.for.adopting.the.notion.of.global.indiscriminability.in.order.to.characterise.the. relation.of.appearing.to.be.the.same.colour.are.discussed.by.Clark.(1993:.56–62) 36.Introducing.the.notion.of.a.colour.that.an.object.appears.to.have.visually.does.not. involve.any.philosophical.stance.regarding.this.appearance .Whatever.this.appearance.may. turn.out.to.be,.here.I.am.only.showing.that.there.is.a.way.to.provide.a.description.of.it.by. analysing.subjects'.discriminatory.responses 37.This.terminology.is.provided.by.Strawson.(1989) .See.also.Sellars.(1963:.93–94,. 192-93).and.Clark.(2000:.6) 38.A. typology.of. this.kind. is. suggested.by.Peacocke. (1984:.349–350),.and. further. elaborated.by.Millar.(1991:.25–31) 52 Prolegomena 7 (1) 2008 sees.a.grey.patch.on.a.yellow.background,.we.would.say.that.he.is.having.the.type.of.experience.that.a.reddish.patch.would.produce.in.certain. circumstances The.typology.I.have.just.described.suggests.a.correspondence.between. the.colour.that.an.object.appears.to.have.and.the.qualitative.property.that. specifies.a.type.of.colour.experience .In.this.account,.if.a.stimulus.looks.to. the.subject.to.be.the.same.colour.as.a.certain.paradigmatic.stimulus,.then. the.subject.has.the.type.of.colour.experience.that.would.be.produced.by. the.paradigmatic.stimulus .Thus.an.individual.S.has.a.colour.experience. with.a.certain.qualitative.property.when.something.appears.to.S.to.have. the.same.colour.as.the.paradigmatic.stimulus The.descriptions.provided.by.a.colour.space.can.be.used.to.categorise. colour.experiences;. indeed,. the.points. in. the.colour. space. represent. the. colours.that.objects.appear.to.have .Thus,.for.every.colour.described.by. the.colour.space,.one.can.associate.a.corresponding.description.of.a.certain.type.of.colour.experience .For.instance,.let.us.assume.that.a.certain. shade.is.represented.in.a.colour.space.by.the.position.XYZ 39.The.description.XYZ.specifies.values.of.hue,.saturation.and.brightness.in.terms.of.a. system.of.relations.of.similarity.with.other.colours .The.relative.type.of. colour.experience.will,.therefore,.be.described.as.the.type.of.experience. someone.has.when.something.looks.XYZ.to.him To.sum.up,.it.seems.we.can.provide.a.clear.enough.account.of.how. contemporary. science. categorises. colour. experiences. and. describes. the. properties.that.ground.this.categorisation .However,.we.still.need.to.establish.whether.these.descriptions.can.help.in.formulating.an.intelligible. version.of.the.knowledge.argument.that.can.be.used.against.a.plausible,. relevant.version.of.modest.physicalism 6. Mary's Scientific Knowledge In. order. to. characterise. Mary's. scientific. knowledge,. some. remaining. issues. must. be. considered . First. of. all,. we. need. to. determine. how. the. categorisation. of. colour. experiences. discussed. above. might. fit. into. the. modest.physicalist.programme.I.recommended.in.section.three .This.requires.showing.how.these.descriptions.can.be.unified.with.the.study.of.the. macroscopic.physical.features.of.the.brain .Contemporary.science.offers. some.hints 39.Each. term.referring. to.a.shade.of.colour.can.be.defined.by.a.description.which. refers.only.to.the.relations.of.similarity.(and.of.opponency.and.composition).represented. by.the.colour.space .This.can.be.achieved.using.a.logical.technique.that.involves."Ramsey. sentences" .For.more.details,.see.Clark.(2000:.256–257) 53L. MALATESTI: Mary's Scientific Knowledge Scientists. aim. to. explain. the. structure. of. colour. quality. spaces. by. means.of.neuro-physiological.mechanisms.that.generate.the.relations.between.points.in.a.quality.space 40.For.example,.the.opponent processors. theory.explains. the.structure.of.a.colour.solid,.and. thereby. the. location. of. any.colour. shade.within. it,. in. terms.of. the. activity.of. certain.neural. mechanisms 41.Groups.of.neurons,.by.virtue.of.their.excitatory.and.inhibitory.connections,.manifest.regular.response.patterns.to.the.outputs.of.three. different.types.of.photoreceptors.in.the.retina .These.opponent.processors. have.a.positive.response.to.stimuli.in.a.certain.part.of.the.spectrum,.and.a. negative.response.to.those.in.other.parts.of.it .Based.on.certain.empirical. evidence,.it.is.assumed.that.there.are.two.chromatic.opponent.processors. (blue-yellow.and.red-green).and.one.achromatic.one.(white-black) .These. three.opponent.processors.generate.the.three.axes.of.the.colour.solid .In. fact,. the.different.activation.of.each.of. these.processors,. resulting. from. a.determinate.stimulation.of.the.photoreceptors.in.the.retina,.defines.the. position.of.a.certain.shade.with.respect.of.each.of.the.solid's.axes .A.very. bright.orange,. for.example,.will. result. from.combined.activation.of. the. neural.processes.correlated.with.the.experience.of.red,.yellow.and.white. and.inhibition.of.the.correlates.of.green,.blue.and.black So. far. we. do. not. have. an. account. of. Mary's. scientific. knowledge. which.is.specific.enough.to.offer.an.intelligible.version.of.the.knowledge. argument .In.fact,.we.have.some.idea.of.how.the.categorisation.of.colour. experiences.by.means.of. certain. colour. spaces. can.be. a. descriptive. requirement.for.a.modest.physicalist.programme.in.the.philosophy.of.mind . Yet. although. we. can. grasp. the. programmatic. lines. of. this. position,. we. may.be.concerned. that. even.our.knowledge.of. the.brain's.macroscopic. features.and.processes. is. far. from.complete .However,. it.has.been.seen. that.we.might.have.a.satisfactory.grasp.of.a.scientific.way.of.describing. the.features.that.ground.a.categorisation.of.colour.experiences .Such.descriptions.offer.the.basic.data.that.neuroscience.is.assumed.to.be.able.to. explain .Thus.we.could.use.a.version.of.the.knowledge.argument.to.test.a. substantive.formulation.of.physicalism,.by.focusing.on.the.capacity.of.this. descriptive.apparatus.to.account.for.properties.that.ground.the.categorisation.of.colour.experiences .Approaching.this.task.requires.some.further.clarification,.as.the.determination.of.colour.solids.is.far.from.complete.at.present .One.reason. 40.In.ordinary.scientific.practice,.the.phenomena.described.by.psychophysics.are.often.used.to.postulate.relative.neural.mechanisms .On.the.general.logical.structure.of.these. inferences,.see.Teller.(1984) 41.Hurvich.(1981).offers.a.comprehensive.and.detailed.presentation.of.this.theory.by. one.of.its.most.important.advocates .See.also.De.Valois.and.De.Valois.(1975:.100–110) . Simplified.accounts.of.the.theory.can.be.found.in.Hardin.(1988).and.Clark.(1993) 54 Prolegomena 7 (1) 2008 is.that.the.set.of.discriminatory.judgements.required.to.achieve.this.aim. is. so. large. that. its. study. is. technically. impossible 42.Secondly,. it.might. not. be. the. case. that. a. three-dimensional. space,. such. as. a. colour. solid,. would.provide.an.exhaustive.description.of.colour.experiences 43.In.fact,. a.three-dimensional.colour.solid.is.obtained.by.examining.colour.stimuli. seen.under.specific.laboratory.conditions .However,.as.Clark.points.out,. "glossy. surfaces,. reflections,. translucency,. transparency,. shadows,. and. mists.all.require.dimensions.of.variations.in.appearance.beyond.the.three. sufficient.for.coloured.surfaces.or.lights.presented.in.the.lab".(Clark.2000:. 7) .Nonetheless,.the.general.nature.of.the.methods.which.might.be.used. to.offer.a.complete.description.of.the.colours.that.objects.appear.to.have. is.clear.enough .The.scope.of.this.approach.is.to.determine,.using.a.set.of. discriminatory.judgements,.the.sensory.dimensions.by.which.subjects.can. discriminate.colours .Once.these.dimensions.are.determined,.it.is.possible. to.derive.a.qualitative.space We.can.now.assume.that.Mary.knows.how.colours.look.to.subjects. in.terms.of.their.positions.in.a.completed.qualitative.space .We.can,.therefore,. ascribe. to. her. a. certain. type. of. intelligible. scientific. knowledge . Mary.can.have.complete.scientific.knowledge.without.having.had.colour. experiences .The.main.notions.involved.in.the.psychophysical.categorisation.of.colour.experiences.are.provided.by.a.colour.space.obtained.from. certain. statistical. procedures. using. discriminatory. judgements. concerning.certain.stimuli .It.seems.that.none.of.these.notions.requires.actually. undergoing. colour. experiences. in. order. to. be. completely. understood . A.colour. space. is.a.geometrical. representation.of. the.dimensions.along. which. subjects.discriminate. colours .We.can.concede. that.Mary.has. an. n-dimensional.model.of. the.different.colours .Moreover,.she.knows. the. typology.of.colour.experiences.derivable.from.such.a.colour.space .This. model.gives.her.information.about.the.dimensions.in.which.light.stimuli. are.categorised.by.the.visual.system .Understanding.that.the.visual.system. enables.certain.kinds.of.discrimination.along.these.dimensions.does.not. seem.to.require.actually.having.colour.experiences .Mary.will.know.that. these.dimensions.result.from.the.application.of.certain.statistical.methods. to.sets.of.discriminatory.responses,.or.judgements.of.similarity,.elicited.by. certain.physical.stimuli .In.particular,.similar.procedures.can.tell.scientists. about.the.dimensions.along.which.a.certain.species'.sensory.system.cat42.For.example,. if.we.consider. just.20.stimuli,.190.rankings.of.similarities.among. pairs.are.needed.to.fill.out.the.data.matrix.for.determining.a.relative.quality.space .Each. such.ranking.may.require.many.trials .It.is.assumed.that.human.subjects.can.discriminate. ten.million.colours;.therefore,.the.determination.of.only.one.percent.of.this.space.would. require.five.billion.similarity.rankings .See.Clark.(1993:.118) 43.See.Clark.(2000:.39) 55L. MALATESTI: Mary's Scientific Knowledge egorises.certain.stimuli .In.particular,.these.procedures.can.be.applied.to. species.with.sensory.systems.that.human.beings.do.not.share,.such.as,.for. instance,.those.involved.in.echolocation Understanding. the. notion. of. a. discriminatory. response. in. psychophysics. does. not. require. having. colour. experiences . Mary. understands. that.these.responses.are.observable.behaviours,.such.as.a.subject's.verbal. reports.on.the.similarities.and.differences.between.certain.physical.stimuli . In.particular,.she.knows.that. these.responses.have. to.satisfy.certain. statistical.conditions.in.order.to.count.as.reliable.evidence.of.subjects'.discriminatory.capacities .Nevertheless,.none.of.these.requirements.implies. that.she.cannot.exhaustively.observe.these.responses.on.a.black-and-white. screen Given.the.statistical.nature.of.the.psychophysical.investigation.of.colour.categorisation,. stimuli.must.be. repeatable. types .Mary,. in. line.with. contemporary.science,.can.regard.these.types.as.defined.by.physical.properties.described.in.the.electromagnetic.theory.of.light .In.particular,.stimuli.are.characterised.in.terms.of.the.intensity.and.wavelength.composition. of.the.light.imaged.on.the.retina .Mary.can.have.an.understanding.of.these. features.from.her.reading.of.physics.books .In.addition,.she.can.detect.and. measure.them.with.instruments.which.we.already.possess,.whose.use.does. not.require.having.colour.experiences Finally,.we.can.formulate.a.version.of.the.knowledge.argument.which. represents.an.intelligible.objection.to.a.substantial.formulation.of.a.physicalist. programme. within. the. boundaries. of. contemporary. science .The. first.premise.of.this.formulation.of.the.knowledge.argument.is.that,.before. her.release,.Mary.can.refer.to.the.properties.that.ground.the.categorisation. of.colour.experiences.using.the.descriptions.offered.by.completed.colour. spaces .The.second.premise.states.that.Mary,.by.seeing.a.coloured.object. after.her.release,.acquires.new knowledge about.colour.experiences .This. knowledge.concerns.the.occurrence.of.qualia,.i e features.of.colour.experiences.which,.from.the.perspective.acquired.by.seeing.colours,.ground. a.categorisation.of.colour.experiences .Thus.a.generalisation.of. the.descriptive.apparatus.of. the.contemporary.science.of.colour.vision.cannot. accommodate.qualia,.and.the.modest.programme.that.I.have.delineated.as. a.plausible.and.relevant.version.of.physicalism.is,.therefore,.untenable Establishing.whether.this.version.of.the.knowledge.argument.is.sound. must.be.left.for.another.occasion .I.will.limit.myself.here.to.showing.that. this. reasoning. is. immune. to. Dennett's. "blue. banana. trick" .As. seen. in. the.second.section.of.this.paper,.Dennett.suggested.that.Mary's.scientific. knowledge.might.enable.her.to.know.what.it.is.like.to.see.colours.prior. to.her.release .In.particular,.she.would.be.able.to.recognise.on.her.release. that.a.blue.banana.has.the.wrong.colour .However,.this.is.not.plausible.in. 56 Prolegomena 7 (1) 2008 the.version.of.the.knowledge.argument.that.I.have.advanced.in.this.paper . Before.her.release,.Mary.knows.how.blue.and.yellow.things.look.in.terms. of.the.positions.of.yellow.and.blue.in.the.system.of.relations.of.similarity. embedded.in.the.complete.colour.space .On.seeing.a.blue.banana,.however,.Mary.can.have.only.very. limited.relational. information.about. this. object's.colour .The.only.relations.of.similarity.and.difference.she.might. actually.discriminate.are.those.between.the.banana's.appearance.and.the. background .Such.evidence.is.insufficient.for.her.to.know.which.colour. she.is.seeing,.and.hence.the.type.of.colour.experience.she.is.having 7. Conclusion I.have.endorsed.Daniel.Dennett's.criticism.of.Frank.Jackson's.version.of. the.knowledge.argument,.according.to.which.Jackson.makes.use.of.an.unintelligible.premise.concerning.Mary's.complete.scientific.knowledge.of. colour.experiences .However,.I.have.also.argued.that.we.should.not.abandon.the.strategy.implicit.in.the.knowledge.argument,.offering.a.substantial. and.understandable.formulation.of.Mary's.relevant.knowledge.of.colour. experiences .This.knowledge.fits.with.a.plausible.and.intelligible.version. of.physicalism.in.the.philosophy.of.mind .Whether.the.resulting.version. of.the.knowledge.argument.is.sound.remains.to.be.seen References Alter,.T .1999 ."The.Knowledge.Argument",.available.at:.http://host uniroma3 it/progetti/kant/field/ka html Byrne,.A .and.Hilbert,.D .2003 ."Color.Realism.and.Color.Science",.Behavioral and Brain Sciences 26:.3–64 Carnap,.R . 1967 .The Logical Structure of the World. (Berkeley:.University.of. 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