byAristotletranslatedbyJ。I。Beare
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HAVINGnowdefinitelyconsideredthesoul，byitself，anditsseveralfaculties，wemustnextmakeasurveyofanimalsandalllivingthings，inordertoascertainwhatfunctionsarepeculiar，andwhatfunctionsarecommon，tothem。Whathasbeenalreadydeterminedrespectingthesoul[sc。byitself]mustbeassumedthroughout。Theremainingparts[sc。theattributesofsoulandbodyconjointly]ofoursubjectmustbenowdealtwith，andwemaybeginwiththosethatcomefirst。
Themostimportantattributesofanimals，whethercommontoallorpeculiartosome，are，manifestly，attributesofsoulandbodyinconjunction，e。g。sensation，memory，passion，appetiteanddesireingeneral，and，inadditionpleasureandpain。Forthesemay，infact，besaidtobelongtoallanimals。Butthereare，besidesthese，certainotherattributes，ofwhichsomearecommontoalllivingthings，whileothersarepeculiartocertainspeciesofanimals。Themostimportantofthesemaybesummedupinfourpairs，viz。wakingandsleeping，youthandoldage，inhalationandexhalation，lifeanddeath。Wemustendeavourtoarriveatascientificconceptionofthese，determiningtheirrespectivenatures，andthecausesoftheiroccurrence。
ButitbehovesthePhysicalPhilosophertoobtainalsoaclearviewofthefirstprinciplesofhealthanddisease，inasmuchasneitherhealthnordiseasecanexistinlifelessthings。Indeedwemaysayofmostphysicalinquirers，andofthosephysicianswhostudytheirartphilosophically，thatwhiletheformercompletetheirworkswithadisquisitiononmedicine，thelatterusuallybasetheirmedicaltheoriesonprinciplesderivedfromPhysics。
Thatalltheattributesaboveenumeratedbelongtosoulandbodyinconjunction，isobvious；fortheyalleitherimplysensationasaconcomitant，orhaveitastheirmedium。Someareeitheraffectionsorstatesofsensation，others，meansofdefendingandsafe—guardingit，whileothers，again，involveitsdestructionornegation。Nowitisclear，alikebyreasoningandobservation，thatsensationisgeneratedinthesoulthroughthemediumofthebody。
Wehavealready，inourtreatiseOntheSoul，explainedthenatureofsensationandtheactofperceivingbysense，andthereasonwhythisaffectionbelongstoanimals。Sensationmust，indeed，beattributedtoallanimalsassuch，forbyitspresenceorabsencewedistinguishessentiallybetweenwhatisandwhatisnotananimal。
Butcomingnowtothespecialsensesseverally，wemaysaythattouchandtastenecessarilyappertaintoallanimals，touch，forthereasongiveninOntheSoul，andtaste，becauseofnutrition。Itisbytastethatonedistinguishesinfoodthepleasantfromtheunpleasant，soastofleefromthelatterandpursuetheformer：andsavouringeneralisanaffectionofnutrientmatter。
Thesenseswhichoperatethroughexternalmedia，viz。smelling，hearing，seeing，arefoundinallanimalswhichpossessthefacultyoflocomotion。Toallthatpossessthemtheyareameansofpreservation；
theirfinalcausebeingthatsuchcreaturesmay，guidedbyantecedentperception，bothpursuetheirfood，andshunthingsthatarebadordestructive。Butinanimalswhichhavealsointelligencetheyservefortheattainmentofahigherperfection。Theybringintidingsofmanydistinctivequalitiesofthings，fromwhichtheknowledgeoftruth，speculativeandpractical，isgeneratedinthesoul。
Ofthetwolastmentioned，seeing，regardedasasupplyfortheprimarywantsoflife，andinitsdirecteffects，isthesuperiorsense；butfordevelopingintelligence，andinitsindirectconsequences，hearingtakestheprecedence。Thefacultyofseeing，thankstothefactthatallbodiesarecoloured，bringstidingsofmultitudesofdistinctivequalitiesofallsorts；whenceitisthroughthissenseespeciallythatweperceivethecommonsensibles，viz。
figure，magnitude，motion，number：whilehearingannouncesonlythedistinctivequalitiesofsound，and，tosomefewanimals，thosealsoofvoice。indirectly，however，itishearingthatcontributesmosttothegrowthofintelligence。Forrationaldiscourseisacauseofinstructioninvirtueofitsbeingaudible，whichitis，notdirectly，butindirectly；sinceitiscomposedofwords，andeachwordisathought—symbol。Accordingly，ofpersonsdestitutefrombirthofeithersense，theblindaremoreintelligentthanthedeafanddumb。
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Ofthedistinctivepotencyofeachofthefacultiesofsenseenoughhasbeensaidalready。
Butastothenatureofthesensoryorgans，orpartsofthebodyinwhicheachofthesensesisnaturallyimplanted，inquirersnowusuallytakeastheirguidethefundamentalelementsofbodies。Not，however，findingiteasytocoordinatefivesenseswithfourelements，theyareatalossrespectingthefifthsense。Buttheyholdtheorganofsighttoconsistoffire，beingpromptedtothisviewbyacertainsensoryaffectionofwhosetruecausetheyareignorant。
Thisisthat，whentheeyeispressedormoved，fireappearstoflashfromit。Thisnaturallytakesplaceindarkness，orwhentheeyelidsareclosed，forthen，too，darknessisproduced。
Thistheory，however，solvesonequestiononlytoraiseanother；
for，unlessonthehypothesisthatapersonwhoisinhisfullsensescanseeanobjectofvisionwithoutbeingawareofit，theeyemustonthistheoryseeitself。Butthenwhydoestheaboveaffectionnotoccuralsowhentheeyeisatrest？Thetrueexplanationofthisaffection，whichwillcontaintheanswertoourquestion，andaccountforthecurrentnotionthattheeyeconsistsoffire，mustbedeterminedinthefollowingway：Thingswhicharesmoothhavethenaturalpropertyofshiningindarkness，without，however，producinglight。Now，thepartoftheeyecalled’theblack’，i。e。itscentralpart，ismanifestlysmooth。Thephenomenonoftheflashoccursonlywhentheeyeismoved，becauseonlythencoulditpossiblyoccurthatthesameoneobjectshouldbecomeasitweretwo。Therapidityofthemovementhastheeffectofmakingthatwhichseesandthatwhichisseenseemdifferentfromoneanother。Hencethephenomenondoesnotoccurunlessthemotionisrapidandtakesplaceindarkness。Foritisinthedarkthatthatwhichissmooth，e。g。theheadsofcertainfishes，andthesepiaofthecuttle—fish，naturallyshines，and，whenthemovementoftheeyeisslow，itisimpossiblethatthatwhichseesandthatwhichisseenshouldappeartobesimultaneouslytwoandone。But，infact，theeyeseesitselfintheabovephenomenonmerelyasitdoessoinordinaryopticalreflexion。
Ifthevisualorganproperreallywerefire，whichisthedoctrineofEmpedocles，adoctrinetaughtalsointheTimaeus，andifvisionweretheresultoflightissuingfromtheeyeasfromalantern，whyshouldtheeyenothavehadthepowerofseeingeveninthedark？Itistotallyidletosay，astheTimaeusdoes，thatthevisualraycomingforthinthedarknessisquenched。Whatisthemeaningofthis’quenching’oflight？Thatwhich，likeafireofcoalsoranordinaryflame，ishotanddryis，indeed，quenchedbythemoistorcold；butheatanddrynessareevidentlynotattributesoflight。Oriftheyareattributesofit，butbelongtoitinadegreesoslightastobeimperceptibletous，weshouldhaveexpectedthatinthedaytimethelightofthesunshouldbequenchedwhenrainfalls，andthatdarknessshouldprevailinfrostyweather。Flame，forexample，andignitedbodiesaresubjecttosuchextinction，butexperienceshowsthatnothingofthissorthappenstothesunlight。
Empedoclesattimesseemstoholdthatvisionistobeexplainedasabovestatedbylightissuingforthfromtheeye，e。g。inthefollowingpassage：—
Aswhenonewhopurposesgoingabroadpreparesalantern，Agleamoffireblazingthroughthestormynight，Adjustingthereto，toscreenitfromallsortsofwinds，transparentsides，Whichscatterthebreathofthewindsastheyblow，While，outthroughthemleaping，thefire，i。e。allthemoresubtilepartofthis，Shinesalonghisthresholdoldincessantbeams：
So[Divinelove]embeddedtheround\"lens\"，[viz。]
theprimaevalfirefencedwithinthemembranes，In[itsown]delicatetissues；
Andthesefendedoffthedeepsurroundingflood，Whileleapingforththefire，i。e。allitsmoresubtilepart—。
Sometimesheaccountsforvisionthus，butatothertimesheexplainsitbyemanationsfromthevisibleobjects。
Democritus，ontheotherhand，isrightinhisopinionthattheeyeisofwater；not，however，whenhegoesontoexplainseeingasmeremirroring。Themirroringthattakesplaceinaneyeisduetothefactthattheeyeissmooth，anditreallyhasitsseatnotintheeyewhichisseen，butinthatwhichsees。Forthecaseismerelyoneofreflexion。Butitwouldseemthateveninhistimetherewasnoscientificknowledgeofthegeneralsubjectoftheformationofimagesandthephenomenaofreflexion。Itisstrangetoo，thatitneveroccurredtohimtoaskwhy，ifhistheorybetrue，theeyealonesees，whilenoneoftheotherthingsinwhichimagesarereflecteddoso。
True，then，thevisualorganproperiscomposedofwater，yetvisionappertainstoitnotbecauseitissocomposed，butbecauseitistranslucent—apropertycommonaliketowaterandtoair。Butwaterismoreeasilyconfinedandmoreeasilycondensedthanair；
whereforeitisthatthepupil，i。e。theeyeproper，consistsofwater。Thatitdoessoisprovedbyfactsofactualexperience。Thesubstancewhichflowsfromeyeswhendecomposingisseentobewater，andthisinundevelopedembryosisremarkablycoldandglistening。Insanguineousanimalsthewhiteoftheeyeisfatandoily，inorderthatthemoistureoftheeyemaybeproofagainstfreezing。Whereforetheeyeisofallpartsofthebodytheleastsensitivetocold：nooneeverfeelscoldinthepartshelteredbytheeyelids。Theeyesofbloodlessanimalsarecoveredwithahardscalewhichgivesthemsimilarprotection。
Itis，tostatethemattergenerally，anirrationalnotionthattheeyeshouldseeinvirtueofsomethingissuingfromit；thatthevisualrayshouldextenditselfallthewaytothestars，orelsegooutmerelytoacertainpoint，andtherecoalesce，assomesay，withrayswhichproceedfromtheobject。Itwouldbebettertosupposethiscoalescencetotakeplaceinthefundamentoftheeyeitself。Buteventhiswouldbemeretrifling。Forwhatismeantbythe’coalescence’oflightwithlight？Orhowisitpossible？Coalescencedoesnotoccurbetweenanytwothingstakenatrandom。Andhowcouldthelightwithintheeyecoalescewiththatoutsideit？Fortheenvironingmembranecomesbetweenthem。
Thatwithoutlightvisionisimpossiblehasbeenstatedelsewhere；
but，whetherthemediumbetweentheeyeanditsobjectsisairorlight，visioniscausedbyaprocessthroughthismedium。
Accordingly，thattheinnerpartoftheeyeconsistsofwateriseasilyintelligible，waterbeingtranslucent。
Now，asvisionoutwardlyisimpossiblewithout[extra—organic]
light，soalsoitisimpossibleinwardly[withoutlightwithintheorgan]。Theremust，therefore，besometranslucentmediumwithintheeye，and，asthisisnotair，itmustbewater。Thesouloritsperceptivepartisnotsituatedattheexternalsurfaceoftheeye，butobviouslysomewherewithin：whencethenecessityoftheinterioroftheeyebeingtranslucent，i。e。capableofadmittinglight。Andthatitissoisplainfromactualoccurrences。Itismatterofexperiencethatsoldierswoundedinbattlebyaswordslashonthetemple，soinflictedastoseverthepassagesof[i。e。inwardfrom]
theeye，feelasuddenonsetofdarkness，asifalamphadgoneout；
becausewhatiscalledthepupil，i。e。thetranslucent，whichisasortofinnerlamp，isthencutoff[fromitsconnexionwiththesoul]。
Hence，ifthefactsbeatallasherestated，itisclearthat—ifoneshouldexplainthenatureofthesensoryorgansinthisway，i。e。bycorrelatingeachofthemwithoneofthefourelements，—wemustconceivethatthepartoftheeyeimmediatelyconcernedinvisionconsistsofwater，thatthepartimmediatelyconcernedintheperceptionofsoundconsistsofair，andthatthesenseofsmellconsistsoffire。（Isaythesenseofsmell，nottheorgan。）Fortheorganofsmellisonlypotentiallythatwhichthesenseofsmell，asrealized，isactually；sincetheobjectofsenseiswhatcausestheactualizationofeachsense，sothatit（thesense）must（attheinstantofactualization）be（actually）thatwhichbefore（themomentofactualization）itwaspotentially。Now，odourisasmoke—likeevaporation，andsmoke—likeevaporationarisesfromfire。
Thisalsohelpsustounderstandwhytheolfactoryorganhasitsproperseatintheenvironmentofthebrain，forcoldmatterispotentiallyhot。Inthesamewaymustthegenesisoftheeyebeexplained。Itsstructureisanoffshootfromthebrain，becausethelatteristhemoistestandcoldestofallthebodilyparts。
Theorganoftouchproperconsistsofearth，andthefacultyoftasteisaparticularformoftouch。Thisexplainswhythesensoryorganofbothtouchandtasteiscloselyrelatedtotheheart。Fortheheartasbeingthehottestofallthebodilyparts，isthecounterpoiseofthebrain。
Thisthenisthewayinwhichthecharacteristicsofthebodilyorgansofsensemustbedetermined。
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Ofthesensiblescorrespondingtoeachsensoryorgan，viz。colour，sound，odour，savour，touch，wehavetreatedinOntheSoulingeneralterms，havingtheredeterminedwhattheirfunctionis，andwhatisimpliedintheirbecomingactualizedinrelationtotheirrespectiveorgans。Wemustnextconsiderwhataccountwearetogiveofanyoneofthem；what，forexample，weshouldsaycolouris，orsound，orodour，orsavour；andsoalsorespecting[theobjectof]touch。Webeginwithcolour。
Now，eachofthemmaybespokenoffromtwopointsofview，i。e。
eitherasactualoraspotential。WehaveinOntheSoulexplainedinwhatsensethecolour，orsound，regardedasactualized[forsensation]isthesameas，andinwhatsenseitisdifferentfrom，thecorrelativesensation，theactualseeingorhearing。Thepointofourpresentdiscussionis，therefore，todeterminewhateachsensibleobjectmustbeinitself，inordertobeperceivedasitisinactualconsciousness。
WehavealreadyinOntheSoulstatedofLightthatitisthecolouroftheTranslucent，[beingsorelatedtoit]incidentally；forwheneverafieryelementisinatranslucentmediumpresencethereisLight；whiletheprivationofitisDarkness。Butthe’Translucent’，aswecallit，isnotsomethingpeculiartoair，orwater，oranyotherofthebodiesusuallycalledtranslucent，butisacommon’nature’andpower，capableofnoseparateexistenceofitsown，butresidinginthese，andsubsistinglikewiseinallotherbodiesinagreaterorlessdegree。Asthebodiesinwhichitsubsistsmusthavesomeextremeboundingsurface，sotoomustthis。Here，then，wemaysaythatLightisa’nature’inheringintheTranslucentwhenthelatteriswithoutdeterminateboundary。Butitismanifestthat，whentheTranslucentisindeterminatebodies，itsboundingextrememustbesomethingreal；andthatcolourisjustthis’something’weareplainlytaughtbyfacts—colourbeingactuallyeitherattheexternallimit，orbeingitselfthatlimit，inbodies。HenceitwasthatthePythagoreansnamedthesuperficiesofabodyits’hue’，for’hue’，indeed，liesatthelimitofthebody；butthelimitofthebody；isnotarealthing；ratherwemustsupposethatthesamenaturalsubstancewhich，externally，isthevehicleofcolourexists[assuchapossiblevehicle]alsointheinteriorofthebody。
Airandwater，too[i。e。aswellasdeterminatelyboundedbodies]
areseentopossesscolour；fortheirbrightnessisofthenatureofcolour。Butthecolourwhichairorseapresents，sincethebodyinwhichitresidesisnotdeterminatelybounded，isnotthesamewhenoneapproachesandviewsitclosebyasitiswhenoneregardsitfromadistance；whereasindeterminatebodiesthecolourpresentedisdefinitelyfixed，unless，indeed，whentheatmosphericenvironmentcausesittochange。Henceitisclearthatthatinthemwhichissusceptibleofcolourisinbothcasesthesame。ItisthereforetheTranslucent，accordingtothedegreetowhichitsubsistsinbodies（anditdoessoinallmoreorless），thatcausesthemtopartakeofcolour。Butsincethecolourisattheextremityofthebody，itmustbeattheextremityoftheTranslucentinthebody。WhenceitfollowsthatwemaydefinecolourasthelimitoftheTranslucentindeterminatelyboundedbody。Forwhetherweconsiderthespecialclassofbodiescalledtranslucent，aswaterandsuchothers，ordeterminatebodies，whichappeartopossessafixedcolouroftheirown，itisattheexteriorboundingsurfacethatallalikeexhibittheircolour。
Now，thatwhichwhenpresentinairproduceslightmaybepresentalsointheTranslucentwhichpervadesdeterminatebodies；oragain，itmaynotbepresent，buttheremaybeaprivationofit。
Accordingly，asinthecaseofairtheoneconditionislight，theotherdarkness，inthesamewaythecoloursWhiteandBlackaregeneratedindeterminatebodies。
Wemustnowtreatoftheothercolours，reviewingtheseveralhypothesesinventedtoexplaintheirgenesis。
（1）ItisconceivablethattheWhiteandtheBlackshouldbejuxtaposedinquantitiessominutethat[aparticleof]eitherseparatelywouldbeinvisible，thoughthejointproduct[oftwoparticles，ablackandawhite]wouldbevisible；andthattheyshouldthushavetheothercoloursforresultants。Theirproductcould，atallevents，appearneitherwhitenorblack；and，asitmusthavesomecolour，andcanhaveneitherofthese，thiscolourmustbeofamixedcharacter—infact，aspeciesofcolourdifferentfromeither。Such，then，isapossiblewayofconceivingtheexistenceofapluralityofcoloursbesidestheWhiteandBlack；andwemaysupposethat[ofthis’plurality’]manyaretheresultofa[numerical]ratio；fortheblacksandwhitesmaybejuxtaposedintheratioof3to2orof3
to4，orinratiosexpressiblebyothernumbers；whilesomemaybejuxtaposedaccordingtononumericallyexpressibleratio，butaccordingtosomerelationofexcessordefectinwhichtheblacksandwhitesinvolvedwouldbeincommensurablequantities；and，accordingly，wemayregardallthesecolours[viz。allthosebasedonnumericalratios]asanalogoustothesoundsthatenterintomusic，andsupposethatthoseinvolvingsimplenumericalratios，liketheconcordsinmusic，maybethosegenerallyregardedasmostagreeable；as，forexample，purple，crimson，andsomefewsuchcolours，theirfewnessbeingduetothesamecauseswhichrendertheconcordsfew。Theothercompoundcoloursmaybethosewhicharenotbasedonnumbers。Oritmaybethat，whileallcolourswhatever[exceptblackandwhite]arebasedonnumbers，someareregularinthisrespect，othersirregular；andthatthelatter[thoughnowsupposedtobeallbasedonnumbers]，whenevertheyarenotpure，owethischaractertoacorrespondingimpurityin[thearrangementof]
theirnumericalratios。Thisthenisoneconceivablehypothesistoexplainthegenesisofintermediatecolours。
（2）AnotheristhattheBlackandWhiteappeartheonethroughthemediumoftheother，givinganeffectlikethatsometimesproducedbypaintersoverlayingalessvividuponamorevividcolour，aswhentheydesiretorepresentanobjectappearingunderwaterorenvelopedinahaze，andlikethatproducedbythesun，whichinitselfappearswhite，buttakesacrimsonhuewhenbeheldthroughafogoracloudofsmoke。Onthishypothesis，too，avarietyofcoloursmaybeconceivedtoariseinthesamewayasthatalreadydescribed；
forbetweenthoseatthesurfaceandthoseunderneathadefiniteratiomightsometimesexist；inothercasestheymightstandinnodeterminateratio。To[introduceatheoryofcolourwhichwouldsetallthesehypothesesaside，and]saywiththeancientsthatcoloursareemanations，andthatthevisibilityofobjectsisduetosuchacause，isabsurd。Fortheymust，inanycase，explainsense—perceptionthroughTouch；sothatitwerebettertosayatoncethatvisualperceptionisduetoaprocesssetupbytheperceivedobjectinthemediumbetweenthisobjectandthesensoryorgan；due，thatis，tocontact[withthemediumaffected，]nottoemanations。
Ifweacceptthehypothesisofjuxtaposition，wemustassumenotonlyinvisiblemagnitude，butalsoimperceptibletime，inorderthatthesuccessioninthearrivalofthestimulatorymovementsmaybeunperceived，andthatthecompoundcolourseenmayappeartobeone，owingtoitssuccessivepartsseemingtopresentthemselvesatonce。
Onthehypothesisofsuperposition，however，nosuchassumptionisneedful：thestimulatoryprocessproducedinthemediumbytheuppercolour，whenthisisitselfunaffected，willbedifferentinkindfromthatproducedbyitwhenaffectedbytheunderlyingcolour。Henceitpresentsitselfasadifferentcolour，i。e。asonewhichisneitherwhitenorblack。Sothat，ifitisimpossibletosupposeanymagnitudetobeinvisible，andwemustassumethatthereissomedistancefromwhicheverymagnitudeisvisible，thissuperpositiontheory，too[i。e。
aswellasNo。3infra]，mightpassasarealtheoryofcolour—mixture。Indeed，inthepreviouscasealsothereisnoreasonwhy，topersonsatadistancefromthejuxtaposedblacksandwhites，someonecolourshouldnotappeartopresentitselfasablendofboth。[Butitwouldnotbesoonanearerview]，foritwillbeshown，inadiscussiontobeundertakenlateron，thatthereisnomagnitudeabsolutelyinvisible。
（3）Thereisamixtureofbodies，however，notmerelysuchassomesuppose，i。e。byjuxtapositionoftheirminimalparts，which，owingto[theweaknessofour]sense，areimperceptiblebyus，butamixturebywhichthey[i。e。the’matter’ofwhichtheyconsist]arewhollyblenttogetherbyinterpenetration，aswehavedescribeditinthetreatiseonMixture，wherewedealtwiththissubjectgenerallyinitsmostcomprehensiveaspect。For，onthesuppositionwearecriticizing，theonlytotalscapableofbeingmixedarethosewhicharedivisibleintominimalparts，[e。g。generaintoindividuals]asmen，horses，orthe[variouskindsof]seeds。Forofmankindasawholetheindividualmanissuchaleastpart；ofhorses[asanaggregate]theindividualhorse。Hencebythejuxtapositionoftheseweobtainamixedtotal，consisting[likeatroopofcavalry]ofbothtogether；
butwedonotsaythatbysuchaprocessanyindividualmanhasbeenmixedwithanyindividualhorse。Notinthisway，butbycompleteinterpenetration[oftheirmatter]，mustweconceivethosethingstobemixedwhicharenotdivisibleintominima；anditisinthecaseofthesethatnaturalmixtureexhibitsitselfinitsmostperfectform。
Wehaveexplainedalreadyinourdiscourse’OnMixture’howsuchmixtureispossible。Thisbeingthetruenatureofmixture，itisplainthatwhenbodiesaremixedtheircoloursalsoarenecessarilymixedatthesametime；and[itisnolessplain]thatthisistherealcausedeterminingtheexistenceofapluralityofcolours—notsuperpositionorjuxtaposition。Forwhenbodiesarethusmixed，theirresultantcolourpresentsitselfasoneandthesameatalldistancesalike；notvaryingasitisseennearerorfartheraway。
Colourswillthus，too[aswellasontheformerhypotheses]，bemanyinnumberonaccountofthefactthattheingredientsmaybecombinedwithoneanotherinamultitudeofratios；somewillbebasedondeterminatenumericalratios，whileothersagainwillhaveastheirbasisarelationofquantitativeexcessordefectnotexpressibleinintegers。Andallelsethatwassaidinreferencetothecolours，consideredasjuxtaposedorsuperposed，maybesaidofthemlikewisewhenregardedasmixedinthewayjustdescribed。
Whycolours，aswellassavoursandsounds，consistofspeciesdeterminate[inthemselves]andnotinfinite[innumber]isaquestionwhichweshalldiscusshereafter。
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Wehavenowexplainedwhatcolouris，andthereasonwhytherearemanycolours；whilebefore，inourworkOntheSoul，weexplainedthenatureofsoundandvoice。WehavenexttospeakofOdourandSavour，bothofwhicharealmostthesamephysicalaffection，althoughtheyeachhavetheirbeingindifferentthings。Savours，asaclass，displaytheirnaturemoreclearlytousthanOdours，thecauseofwhichisthattheolfactorysenseofmanisinferiorinacutenesstothatoftheloweranimals，andis，whencomparedwithourothersenses，theleastperfectofMan’ssenseofTouch，onthecontrary，excelsthatofallotheranimalsinfineness，andTasteisamodificationofTouch。
Nowthenaturalsubstancewaterpersetendstobetasteless。But[sincewithoutwatertastingisimpossible]either（a）wemustsupposethatwatercontainsinitself[uniformlydiffusedthroughit]thevariouskindsofsavour，alreadyformed，thoughinamountssosmallastobeimperceptible，whichisthedoctrineofEmpedocles；or（b）thewatermustbeasortofmatter，qualified，asitwere，toproducegermsofsavoursofallkinds，sothatallkindsofsavouraregeneratedfromthewater，thoughdifferentkindsfromitsdifferentparts，orelse（c）thewaterisinitselfquiteundifferentiatedinrespectofsavour[whetherdevelopedorundeveloped]，butsomeagent，suchforexampleasonemightconceiveHeatortheSuntobe，istheefficientcauseofsavour。
（a）Ofthesethreehypotheses，thefalsityofthatheldbyEmpedoclesisonlytooevident。Forweseethatwhenpericarpalfruitsareplucked[fromthetree]andexposedinthesun，orsubjectedtotheactionoffire，theirsapidjuicesarechangedbytheheat，whichshowsthattheirqualitiesarenotduetotheirdrawinganythingfromthewaterintheground，buttoachangewhichtheyundergowithinthepericarpitself；andwesee，moreover，thatthesejuices，whenextractedandallowedtolie，insteadofsweetbecomebylapseoftimeharshorbitter，oracquiresavoursofanyandeverysort；andthat，again，bytheprocessofboilingorfermentationtheyaremadetoassumealmostallkindsofnewsavours。
（b）ItislikewiseimpossiblethatwatershouldbeamaterialqualifiedtogenerateallkindsofSavourgerms[sothatdifferentsavoursshouldariseoutofdifferentpartsofthewater]；forweseedifferentkindsoftastegeneratedfromthesamewater，havingitastheirnutriment。
（C）Itremains，therefore，tosupposethatthewaterischangedbypassivelyreceivingsomeaffectionfromanexternalagent。Now，itismanifestthatwaterdoesnotcontractthequalityofsapidityfromtheagencyofHeatalone。Forwaterisofallliquidsthethinnest，thinnereventhanoilitself，thoughoil，owingtoitsviscosity，ismoreductilethanwater，thelatterbeinguncohesiveinitsparticles；whencewaterismoredifficultthanoiltoholdinthehandwithoutspilling。Butsinceperfectlypurewaterdoesnot，whensubjectedtotheactionofHeat，showanytendencytoacquireconsistency，wemustinferthatsomeotheragencythanheatisthecauseofsapidity。Forallsavours[i。e。sapidliquors]exhibitacomparativeconsistency。Heatis，however，acoagentinthematter。
Nowthesapidjuicesfoundinpericarpalfruitsevidentlyexistalsointheearth。Hencemanyoftheoldnaturalphilosophersassertthatwaterhasqualitieslikethoseoftheearththroughwhichitflows，afactespeciallymanifestinthecaseofsalinesprings，forsaltisaformofearth。Hencealsowhenliquidsarefilteredthroughashes，abittersubstance，thetastetheyyieldisbitter。Therearemanywells，too，ofwhichsomearebitter，othersacid，whileothersexhibitothertastesofallkinds。
Aswastobeanticipated，therefore，itisinthevegetablekingdomthattastesoccurinrichestvariety。For，likeallthingselse，theMoist，bynature’slaw，isaffectedonlybyitscontrary；
andthiscontraryistheDry。ThusweseewhytheMoistisaffectedbyFire，whichasanaturalsubstance，isdry。Heatis，however，theessentialpropertyofFire，asDrynessisofEarth，accordingtowhathasbeensaidinourtreatiseontheelements。FireandEarth，therefore，takenabsolutelyassuch，havenonaturalpowertoaffect，orbeaffectedby，oneanother；norhaveanyotherpairofsubstances。Anytwothingscanaffect，orbeaffectedby，oneanotheronlysofarascontrarietytotheotherresidesineitherofthem。
As，therefore，personswashingColoursorSavoursinaliquidcausethewaterinwhichtheywashtoacquiresuchaquality[asthatofthecolourorsavour]，sonature，too，bywashingtheDryandEarthyintheMoist，andbyfilteringthelatter，thatis，movingitonbytheagencyofheatthroughthedryandearthy，impartstoitacertainquality。Thisaffection，wroughtbytheaforesaidDryintheMoist，capableoftransformingthesenseofTastefrompotentialitytoactuality，isSavour。Savourbringsintoactualexercisetheperceptivefacultywhichpre—existedonlyinpotency。Theactivityofsense—perceptioningeneralisanalogous，nottotheprocessofacquiringknowledge，buttothatofexercisingknowledgealreadyacquired。
ThatSavours，eitherasaqualityorastheprivationofaquality，belongnottoeveryformoftheDrybuttotheNutrient，weshallseebyconsideringthatneithertheDrywithouttheMoist，northeMoistwithouttheDry，isnutrient。Fornosingleelement，butonlycompositesubstance，constitutesnutrimentforanimals。Now，amongtheperceptibleelementsofthefoodwhichanimalsassimilate，thetangiblearetheefficientcausesofgrowthanddecay；itisquahotorcoldthatthefoodassimilatedcausesthese；fortheheatorcoldisthedirectcauseofgrowthordecay。Itisquagustable，however，thattheassimilatedfoodsuppliesnutrition。ForallorganismsarenourishedbytheSweet[i。e。the’gustable’proper]，eitherbyitselforincombinationwithothersavours。OfthiswemustspeakwithmoreprecisedetailinourworkonGeneration：forthepresentweneedtouchuponitonlysofarasoursubjecthererequires。Heatcausesgrowth，andfitsthefood—stuffforalimentation；itattracts[intotheorganicsystem]thatwhichislight[viz。thesweet]，whilethesaltandbitteritrejectsbecauseoftheirheaviness。Infact，whatevereffectsexternalheatproducesinexternalbodies，thesameareproducedbytheirinternalheatinanimalandvegetableorganisms。Henceitis[i。e。bytheagencyofheatasdescribed]thatnourishmentiseffectedbythesweet。Theothersavoursareintroducedintoandblendedinfood[naturally]onaprincipleanalogoustothatonwhichthesalineortheacidisusedartificially，i。e。forseasoning。Theselatterareusedbecausetheycounteractthetendencyofthesweettobetoonutrient，andtofloatonthestomach。
Astheintermediatecoloursarisefromthemixtureofwhiteandblack，sotheintermediatesavoursarisefromtheSweetandBitter；
andthesesavours，too，severallyinvolveeitheradefiniteratio，orelseanindefiniterelationofdegree，betweentheircomponents，eitherhavingcertainintegralnumbersatthebasisoftheirmixture，and，consequently，oftheirstimulativeeffect，orelsebeingmixedinproportionsnotarithmeticallyexpressible。Thetasteswhichgivepleasureintheircombinationarethosewhichhavetheircomponentsjoinedinadefiniteratio。
ThesweettastealoneisRich，[thereforethelattermayberegardedasavarietyoftheformer]，while[sofarasbothimplyprivationoftheSweet]theSalineisfairlyidenticalwiththeBitter。
BetweentheextremesofsweetandbittercometheHarsh，thePungent，theAstringent，andtheAcid。SavoursandColours，itwillbeobserved，containrespectivelyaboutthesamenumberofspecies。Fortherearesevenspeciesofeach，if，asisreasonable，weregardDun[orGrey]asavarietyofBlack（forthealternativeisthatYellowshouldbeclassedwithWhite，asRichwithSweet）；while[theirreduciblecolours，viz。]Crimson，Violet，leek—Green，anddeepBlue，comebetweenWhiteandBlack，andfromtheseallothersarederivedbymixture。
Again，asBlackisaprivationofWhiteintheTranslucent，soSalineorBitterisaprivationofSweetintheNutrientMoist。Thisexplainswhytheashofallburntthingsisbitter；forthepotable[sc。thesweet]moisturehasbeenexudedfromthem。
Democritusandmostofthenaturalphilosopherswhotreatofsense—perceptionproceedquiteirrationally，fortheyrepresentallobjectsofsenseasobjectsofTouch。Yet，ifthisisreallyso，itclearlyfollowsthateachoftheothersensesisamodeofTouch；
butonecanseeataglancethatthisisimpossible。
Again，theytreattheperceptscommontoallsensesaspropertoone。For[thequalitiesbywhichtheyexplaintasteviz。]MagnitudeandFigure，RoughnessandSmoothness，and，moreover，theSharpnessandBluntnessfoundinsolidbodies，areperceptscommontoallthesenses，orifnottoall，atleasttoSightandTouch。Thisexplainswhyitisthatthesensesareliabletoerrregardingthem，whilenosucherrorarisesrespectingtheirpropersensibles；e。g。thesenseofSeeingisnotdeceivedastoColour，noristhatofHearingastoSound。
Ontheotherhand，theyreducethepropertocommonsensibles，asDemocritusdoeswithWhiteandBlack；forheassertsthatthelatteris[amodeofthe]rough，andtheformer[amodeofthe]smooth，whilehereducesSavourstotheatomicfigures。Yetsurelynoonesense，or，ifany，thesenseofSightratherthananyother，candiscernthecommonsensibles。ButifwesupposethatthesenseofTasteisbetterabletodoso，then—sincetodiscernthesmallestobjectsineachkindiswhatmarkstheacutestsense—Tasteshouldhavebeenthesensewhichbestperceivedthecommonsensiblesgenerally，andshowedthemostperfectpowerofdiscerningfiguresingeneral。
Again，allthesensiblesinvolvecontrariety；e。g。inColourWhiteiscontrarytoBlack，andinSavoursBitteriscontrarytoSweet；
butnoonefigureisreckonedascontrarytoanyotherfigure。Else，towhichofthepossiblepolygonalfigures[towhichDemocritusreducesBitter]isthesphericalfigure[towhichhereducesSweet]
contrary？
Again，sincefiguresareinfiniteinnumber，savoursalsoshouldbeinfinite；[thepossiblerejoinder—’thattheyareso，onlythatsomearenotperceived’—cannotbesustained]forwhyshouldonesavourbeperceived，andanothernot？
ThiscompletesourdiscussionoftheobjectofTaste，i。e。Savour；
fortheotheraffectionsofSavoursareexaminedintheirproperplaceinconnectionwiththenaturalhistoryofPlants。