Inordertoanswerouroriginalquestion，letusnow，therefore，assumeoneproposition，whichisclearfromwhatprecedes，viz.thatevenwhentheexternalobjectofperceptionhasdeparted，theimpressionsithasmadepersist，andarethemselvesobjectsofperception：and[letusassume]，besides，thatweareeasilydeceivedrespectingtheoperationsofsense—perceptionwhenweareexcitedbyemotions，anddifferentpersonsaccordingtotheirdifferentemotions;forexample，thecowardwhenexcitedbyfear，theamorouspersonbyamorousdesire;sothat，withbutlittleresemblancetogoupon，theformerthinksheseeshisfoesapproaching，thelatter，thatheseestheobjectofhisdesire;andthemoredeeplyoneisundertheinfluenceoftheemotion，thelesssimilarityisrequiredtogiverisetotheseillusoryimpressions.
Thustoo，bothinfitsofanger，andalsoinallstatesofappetite，allmenbecomeeasilydeceived，andmoresothemoretheiremotionsareexcited.Thisisthereasontoowhypersonsinthedeliriumoffeversometimesthinktheyseeanimalsontheirchamberwalls，anillusionarisingfromthefaintresemblancetoanimalsofthemarkingsthereonwhenputtogetherinpatterns;andthissometimescorrespondswiththeemotionalstatesofthesufferers，insuchawaythat，ifthelatterbenotveryill，theyknowwellenoughthatitisanillusion;butiftheillnessismoreseveretheyactuallymoveaccordingtotheappearances.Thecauseoftheseoccurrencesisthatthefacultyinvirtueofwhichthecontrollingsensejudgesisnotidenticalwiththatinvirtueofwhichpresentationscomebeforethemind.Aproofofthisis，thatthesunpresentsitselfasonlyafootindiameter，thoughoftensomethingelsegainsaysthepresentation.Again，whenthefingersarecrossed，theoneobject[placedbetweenthem]isfelt[bythetouch]astwo;butyetwedenythatitistwo;forsightismoreauthoritativethantouch.Yet，iftouchstoodalone，weshouldactuallyhavepronouncedtheoneobjecttobetwo.Thegroundofsuchfalsejudgementsisthatanyappearanceswhateverpresentthemselves，notonlywhenitsobjectstimulatesasense，butalsowhenthesensebyitselfaloneisstimulated，providedonlyitbestimulatedinthesamemannerasitisbytheobject.Forexample，topersonssailingpastthelandseemstomove，whenitisreallytheeyethatisbeingmovedbysomethingelse[themovingship.]
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Fromthisitismanifestthatthestimulatorymovementsbaseduponsensoryimpressions，whetherthelatterarederivedfromexternalobjectsorfromcauseswithinthebody，presentthemselvesnotonlywhenpersonsareawake，butalsothen，whenthisaffectionwhichiscalledsleephascomeuponthem，withevengreaterimpressiveness.Forbyday，whilethesensesandtheintellectareworkingtogether，they（i.e.suchmovements）areextrudedfromconsciousnessorobscured，justasasmallerisbesidealargerfire，orassmallbesidegreatpainsorpleasures，though，assoonasthelatterhaveceased，eventhosewhicharetriflingemergeintonotice.Butbynight[i.e.insleep]owingtotheinactionoftheparticularsenses，andtheirpowerlessnesstorealizethemselves，whicharisesfromtherefluxofthehotfromtheexteriorpartstotheinterior，they[i.e.theabove\'movements\']areborneintotheheadquartersofsense—perception，andtheredisplaythemselvesasthedisturbance（ofwakinglife）subsides.Wemustsupposethat，likethelittleeddieswhicharebeingeverformedinrivers，sothesensorymovementsareeachacontinuousprocess，oftenremaininglikewhattheywerewhenfirststarted，butoften，too，brokenintootherformsbycollisionswithobstacles.This[lastmentionedpoint]，moreover，givesthereasonwhynodreamsoccurinsleepimmediatelyaftermeals，ortosleeperswhoareextremelyyoung，e.g.toinfants.Theinternalmovementinsuchcasesisexcessive，owingtotheheatgeneratedfromthefood.Hence，justasinaliquid，ifonevehementlydisturbsit，sometimesnoreflectedimageappears，whileatothertimesoneappears，indeed，bututterlydistorted，soastoseemquiteunlikeitsoriginal;while，whenoncethemotionhasceased，thereflectedimagesareclearandplain;inthesamemannerduringsleepthephantasms，orresiduarymovements，whicharebaseduponthesensoryimpressions，becomesometimesquiteobliteratedbytheabovedescribedmotionwhentooviolent;whileatothertimesthesightsareindeedseen，butconfusedandweird，andthedreams[whichthenappear]areunhealthy，likethoseofpersonswhoareatrabilious，orfeverish，orintoxicatedwithwine.Forallsuchaffections，beingspirituous，causemuchcommotionanddisturbance.Insanguineousanimals，inproportionasthebloodbecomescalm，andasitspurerareseparatedfromitslesspureelements，thefactthatthemovement，basedonimpressionsderivedfromeachoftheorgansofsense，ispreservedinitsintegrity，rendersthedreamshealthy，causesa[clear]imagetopresentitself，andmakesthedreamerthink，owingtotheeffectsborneinfromtheorganofsight，thatheactuallysees，andowingtothosewhichcomefromtheorganofhearing，thathereallyhears;andsoonwiththosealsowhichproceedfromtheothersensoryorgans.Foritisowingtothefactthatthemovementwhichreachestheprimaryorganofsensecomesfromthem，thatoneevenwhenawakebelieveshimselftosee，orhear，orotherwiseperceive;justasitisfromabeliefthattheorganofsightisbeingstimulated，thoughinrealitynotsostimulated，thatwesometimeserroneouslydeclareourselvestosee，orthat，fromthefactthattouchannouncestwomovements，wethinkthattheoneobjectistwo.For，asarule，thegoverningsenseaffirmsthereportofeachparticularsense，unlessanotherparticularsense，moreauthoritative，makesacontradictoryreport.Ineverycaseanappearancepresentsitself，butwhatappearsdoesnotineverycaseseemreal，unlesswhenthedecidingfacultyisinhibited，ordoesnotmovewithitspropermotion.