Whatismorallypermissible,andwhatismorallyobligatory?Thesequestionsformthecoreofavastamountofphilosophicalreasoning.InhisFundamentalPrinciplesoftheMetaphysicsofMorals,ImmanuelKantdevelopedabasisfortheanswers.Inthislandmarkwork,theGermanphilosopheraskswhatsortofmaximmightfunctionasaguidetoappropriateactionunderagivensetofcircumstances.Byuniversalizingsuchamaxim,wouldmorallypermissiblebehaviornotbecomeclear?Supposethateveryoneweretobehaveinaccordancewiththismaxim.Ifeveryonefollowedthemaximinthesamewaywithoutharmtocivilizedculture,thenthebehaviorwouldbemorallypermissible.Butwhatifnoonefollowedthemaxim?Wouldcivilizationtherebybeatrisk?Insuchacase,thebehaviorwouldbemorallyobligatory.Kant’stest,knownastheCategoricalImperative,isalogicalproofoftheGoldenRuleandthecenterpieceofthiswork.Itconstituteshisbest-knowncontributiontoethicaldiscussion,andafamiliaritywithhisreasoninginthisbookisessentialtostudentsofphilosophy,religion,andhistory.
