Ihaveseenamillionblackcrows。CanIsaythatthemillionandonethcrowwillbeblack？Toanswerthiswemustaskwhetherblacknessisapropertyof’kind。’79*Iftheblacknessbe，’asitwere，anaccident，’ornotapropertyofkind，itmust，hesays，beacaseofcausation。Ifnotacaseofcausation，itmustbeapropertyofkind。Hencewehavethesingularresult，thatifthecoexistencebecasual，itiscaused，andifinvariable，notcaused。As’causation’meansaccordingtohimsimplyunconditionalconnection，thestatementseemstobeespeciallyparadoxical。Itis，however，explicable。
Theblacknessofthecrowmayberegardedas’accidental，’ifitisduetotheexternalcause。Thecrow，perhaps，hasfallenintoapaint-pot。Theblacknessis’caused，’then，bythepropertiesofpaintandbythe’accidental’collocation。Itisan’accident’inthecrow，thoughcausedinrespectofthegeneralarrangementsoftheuniverse。Butwhy，ifapropertyof’kind，’
shoulditbecalled’notcaused’？HerewehaveacuriousresultofMill’sviewofcausation。Ournaturalreplywouldbethatthecolourisstillcausedaseverythingelseiscaused。80*Weassume，thatis，that’crow’impliessuchaconstitutionthatunderagivenenvironmentcrowswillbeblack。Changesomethingoutsidethecrowandhemayturnwhite。Orfindawhitecrowinthesame’environment，’andweinfersomedifferenceinhisconstitution。Thereisarelation，weassume，thoughwecannotspecifyitsnature，whichdeterminesthecolour，andasinallcaseswehaveatoncecollocationandcausation。HereisMill’speculiardifficulty。Causation，asheisprofoundlyconvinced，alwaysmeansabeginning。Itisonly，aswehaveseen，concernedwithchanges，notwithpersistence。Therefore，iftwothings，likeblacknessandcrowness，existsidebyside，itisacaseofcollocation，andconsequently，ashesupposes，notacaseofcausation。Hecannotrecogniseareciprocalrelation，althoughitisclearthatifonethingisfoundalwaystoaccompanyanother，theargumentisthesameasthoughonealwaysfollowedanother。
Indeed，hiswholetheoryofinductionimpliesthepossibilityofreasoningfromonepropertyorattributetoanother。Makeachangeinoneandtheothermustbechanged。Heseesthisclearlyinthecaseoforganisedbodies。81*Inthatcase，hesays，thereisa’presumption’thatthepropertiesare’derivable’andtherefore’caused，’becausetherewehavesequencesoroneprocessfollowinganother。Hethusseemstolimithis’naturalkinds’chieflytochemicalcompounds。Therewehavepropertieslyingsidebysideandnot’derivable，’thatis，nottobeinferredbyusfromthepropertiesoftheelementaryconstituents。Theveryattempttoderivethemisidle。Asanyeventmaycauseanyother，howeverunlike，soanysetofpropertiesmaybesimplystucktogether。Baconisagainreproved82*forassumingthat’everyobjecthasaninvariablecoexistent。’Theultimateproperties，sofaraswecanconjecture，are’inherentlypropertiesofmanydifferentkindsofthings，notalliedinanyotherrespect。’Theysimplyliesidebyside，withoutreferencetoeachother。ThusMillpusheshisempiricismtoassumingnotonlythatourknowledgeofpropertiesmustrestupondirectobservation，butthatthereisabsolutelynoconnectionor’cause’tobeknown。The’kind’afterall，whichwasmeanttobeanessentialbond，turnsouttobeitselfapurelyarbitrarycollectionofattributes，andwehavetoaskwhetheritdoesnotloseallthesignificancewhichheattachedtoit。The’collocation’meansthattheattributessimplyliesidebyside，andyetarealwaysconjoined。Thetiewhichcombinesthemisundiscoverable，andthereforeforusnon-existent。Itis，asherightlyinsists，importantthatourclassificationshouldcorrespondtonaturalkinds。’Kinds，’hesays，areclasses’betweenwhichthereisanimpassablebarrier’；
thelogicalclassisarbitrary，buttherealclassisanessentialfact，Hisillustrationisremarkable。Heholdsthatthe’speciesofplantsarenotonlyrealkinds，butareprobablyallofthemreallowestkinds，infimaespecies，’andthatfurthersubdivisionwouldleadtonovaluableresults。83*Thedoctrinethatthespeciesofbotanymustcorrespondto’realkinds’iscuriousinawriterwhowashimselfabotanistandfamiliarwiththedifficultyofmakingabsolutedivisionsbetweenkinds。TheconflictwiththeconceptionsimpliedinDarwinismisofthehighestimportance。84*Thedistinctionbetween’kinds，’