vers y ▁The ▁astronom er ▁Jean - B apt iste ▁Mor in ▁was ▁noted ▁as ▁one ▁of ▁the ▁first ▁people ▁to ▁question ▁Des cart es ' ▁method ▁in ▁creating ▁his ▁theories . ▁... Des cart es ▁would ▁not ▁accept ▁Mor in ' s ▁ob jections ▁that ▁the ▁demonstr ations ▁in ▁the ▁D io pt ric ▁are ▁circular ▁or ▁that ▁the ▁proposed ▁explan ations ▁are ▁artificial . ▁He ▁gr ants ▁that ▁' to ▁prove ▁some ▁effects ▁by ▁a ▁certain ▁cause , ▁then ▁to ▁prove ▁this ▁cause ▁by ▁the ▁same ▁effects ', ▁is ▁arg uing ▁in ▁a ▁circle ; ▁but ▁he ▁would ▁not ▁admit ▁that ▁it ▁is ▁circular ▁to ▁explain ▁some ▁effects ▁by ▁a ▁cause , ▁and ▁then ▁to ▁prove ▁that ▁the ▁cause ▁by ▁the ▁same ▁effects , ▁' for ▁there ▁is ▁a ▁great ▁difference ▁between ▁prov ing ▁and ▁explaining '. ▁Des cart es ▁points ▁out ▁that ▁he ▁used ▁the ▁word ▁' dem on str ation ' ... to ▁mean ▁either ▁one ▁or ▁the ▁other ▁' in ▁accord ance ▁with ▁common ▁usage , ▁and ▁not ▁in ▁the ▁particular ▁sense ▁given ▁to ▁it ▁by ▁Philosoph ers '. ▁Then ▁he ▁adds : ▁' it ▁is ▁not ▁a ▁circle ▁to ▁prove ▁a ▁cause ▁by ▁several ▁effects ▁which ▁are ▁known ▁otherwise , ▁then ▁reci proc ally ▁to ▁prove ▁some ▁other ▁effects ▁by ▁this ▁cause '. ▁ ▁References ▁ ▁Category : Work s ▁by ▁René ▁Des cart es ▁Category : History ▁of ▁physics ▁Category : Opt ics <0x0A> </s> ▁John ▁Con way ▁( born ▁ 8 ▁March ▁ 1 9