Destructionsuperveneswhenthedeterminedgetsthebetterofthedeterminingbythehelpoftheenvironment（thoughinaspecialsensethewordputrefactionisappliedtopartialdestruction，whenathing’snatureisperverted）。Henceeverything，exceptfire，isliabletoputrefy;forearth，water，andairputrefy，beingallofthemmatterrelativelytofire。Thedefinitionofputrefactionis：thedestructionofthepeculiarandnaturalheatinanymoistsubjectbyexternalheat，thatis，bytheheatoftheenvironment。Sosincelackofheatisthegroundofthisaffectionandeverythinginasfarasitlacksheatiscold，bothheatandcoldwillbethecausesofputrefaction，whichwillbedueindifferentlytocoldintheputrefyingsubjectortoheatintheenvironment。
Thisexplainswhyeverythingthatputrefiesgrowsdrierandendsbybecomingearthordung。Thesubject’sownheatdepartsandcausesthenaturalmoisturetoevaporatewithit，andthenthereisnothinglefttodrawinmoisture，foritisathing’speculiarheatthatattractsmoistureanddrawsitin。Again，putrefactiontakesplacelessincoldthatinhotseasons，forinwinterthesurroundingairandwatercontainbutlittleheatandithasnopower，butinsummerthereismore。Again，whatisfrozendoesnotputrefy，foritscoldisgreaterthattheheatoftheairandsoisnotmastered，whereaswhataffectsathingdoesmasterit。Nordoesthatwhichisboilingorhotputrefy，fortheheatintheairbeinglessthanthatintheobjectdoesnotprevailoveritorsetupanychange。Sotooanythingthatisflowingorinmotionislessapttoputrefythanathingatrest，forthemotionsetupbytheheatintheairisweakerthanthatpre-existingintheobject，andsoitcausesnochange。Forthesamereasonagreatquantityofathingputrefieslessreadilythanalittle，forthegreaterquantitycontainstoomuchproperfireandcoldforthecorrespondingqualitiesintheenvironmenttogetthebetterof。Hence，theseaputrefiesquicklywhenbrokenupintoparts，butnotasawhole;andallotherwaterslikewise。Animalstooaregeneratedinputrefyingbodies，becausetheheatthathasbeensecreted，beingnatural，organizestheparticlessecretedwithit。
Somuchforthenatureofbecomingandofdestruction。
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Wemustnowdescribethenextkindsofprocesseswhichthequalitiesalreadymentionedsetupinactuallyexistingnaturalobjectsasmatter。