questions about the status of nonhumans. The reason for
this—whichmayalreadybeapparentfromthefirstchapterof
thisbook—hastodowiththewayinwhichtheprincipleof
equality must be interpreted and defended, if it is to be
defended at all.
Forphilosophersofthe1950sand1960s,theproblemwasto
interprettheideathatallhumanbeingsareequalinamanner
that does not make itplainly false.In most ways, human
beingsarenotequal;andifweseeksomecharacteristicthat
allofthempossess,thenthischaracteristicmustbeakindof
lowestcommondenominator,pitchedsolowthatnohuman
beinglacksit.Thecatchisthatanysuchcharacteristicthatis
possessedbyallhumanbeingswillnotbepossessedonlyby
humanbeings.Forexample,allhumanbeings,butnotonly
humanbeings, arecapableoffeeling pain;and whileonly
humanbeingsarecapableofsolvingcomplexmathematical
problems,notallhumanscandothis.Soitturnsoutthatin
theonlysenseinwhichwecantrulysay,asanassertionof
fact, that allhumans are equal, atleast some members of
other species are also “equal”—equal, that is, to some
humans.
If,ontheotherhand,wedecidethat,asIarguedinChapter1,
thesecharacteristicsare reallyirrelevant to theproblem of
equality,andequalitymustbebasedonthemoralprincipleof
equalconsiderationofinterestsratherthanonthepossession
ofsomecharacteristic,itisevenmoredifficulttofindsome
basis for excluding animals from the sphere of equality.
This resultis not what theegalitarianphilosophers of that
periodoriginallyintendedtoassert.Insteadofacceptingthe
outcome to which their own reasonings naturally pointed,