nnot　be　generated　from　something　incorporeal　nor　from　a　body　which　is　not　an　element；　and　the　only　remaining　alternative　is　that　they　are　generated　from　one　another。
  7
  We　must；　therefore；　turn　to　the　question；　what　is　the　manner　of　their　generation　from　one　another？　Is　it　as　Empedocles　and　Democritus　say；　or　as　those　who　resolve　bodies　into　planes　say；　or　is　there　yet　another　possibility？　（1）　What　the　followers　of　Empedocles　do；　though　without　observing　it　themselves；　is　to　reduce　the　generation　of　elements　out　of　one　another　to　an　illusion。　They　make　it　a　process　of　excretion　from　a　body　of　what　was　in　it　all　the　time…as　though　generation　required　a　vessel　rather　than　a　material…so　that　it　involves　no　change　of　anything。　And　even　if　this　were　accepted；　there　are　other　implications　equally　unsatisfactory。　We　do　not　expect　a　mass　of　matter　to　be　made　heavier　by　compression。　But　they　will　be　bound　to　maintain　this；　if　they　say　that　water　is　a　body　present　in　air　and　excreted　from　air；　since　air　becomes　heavier　when　it　turns　into　water。　Again；　when　the　mixed　body　is　divided；　they　can　show　no　reason　why　one　of　the　constituents　must　by　itself　take　up　more　room　than　the　body　did：　but　when　water　turns　into　air；　the　room　occupied　is　increased。　The　fact　is　that　the　finer　body　takes　up　more　room；　as　is　obvious　in　any　case　of　transformation。　As　the　liquid　is　converted　into　vapour　or　air　the　vessel　which　contains　it　is　often　burst　because　it　does　not　contain　room　enough。　Now；　if　there　is　no　void　at　all；　and　if；　as　those　who　take　this　view　say；　there　is　no　expansion　of　bodies；　the　impossibility　of　this　is　manifest：　and　if　there　is　void　and　expansion；　there　is　no　accounting　for　the　fact　that　the　body　which　results　from　division　cfpies　of　necessity　a　greater　space。　It　is　inevitable；　too；　that　generation　of　one　out　of　another　should　come　to　a　stop；　since　a　finite　quantum　cannot　contain　an　infinity　of　finite　quanta。　When　earth　produces　water　something　is　taken　away　from　the　earth；　for　the　process　is　one　of　excretion。　The　same　thing　happens　again　when　the　residue　produces　water。　But　this　can　only　go　on　for　ever；　if　the　finite　body　contains　an　infinity；　which　is　impossible。　Therefore　the　generation　of　elements　out　of　one　another　will　not　always　continue。　　　（2）　We　have　now　explained　that　the　mutual　transformations　of　the　elements　cannot　take　place　by　means　of　excretion。　The　remaining　alternative　is　that　they　should　be　generated　by　changing　into　one　another。　And　this　in　one　of　two　ways；　either　by　change　of　shape；　as　the　same　wax　takes　the　shape　both　of　a　sphere　and　of　a　cube；　or；　as　some　assert；　by　resolution　into　planes。　（a）　Generation　by　change　of　shape　would　necessarily　involve　the　assertion　of　atomic　bodies。　For　if　the　particles　were　divisible　there　would　be　a　part　of　fire　which　was　not　fire　and　a　part　of　earth　which　was　not　earth；　for　the　reason　that　not　every　part　of　a　pyramid　is　a　pyramid　nor　of　a　cube　a　cube。　But　if　（b）　the　process　is　resolution　into　planes；　the　first　difficulty　is　that　the　elements　cannot　all　be　generated　out　of　one　another。　This　they　are　obliged　to　assert；　and　do　assert。　It　is　absurd；　because　it　is　unreasonable　that　one　element　alone　should　have　no　part　in　the　transformations；　and　also　contrary　to　the　observed　data　of　sense；　according　to　which　all　alike　change　into　one　another。　In　fact　their　explanation　of　the　observations　is　not　consistent　with　the　observations。　And　the　reason　is　that　their　ultimate　principles　are　wrongly　assumed：　they　had　certain　predetermined　views；　and　were　resolved　to　bring　everything　into　line　with　them。　It　seems　that　perceptible　things　require　perceptible　principles；　eternal　things　eternal　principles；　corruptible　things　corruptible　principles；　and；　in　general；　every　subject　matter　principles　homogeneous　with　itself。　But　they；　owing　to　their　love　for　their　principles；　fall　into　the　attitude　of　men　who　undertake　the　defence　of　a　position　in　argument。　In　the　confidence　that　the　principles　are　true　they　are　ready　to　accept　any　consequence　of　their　application。　As　though　some　principles　did　not　require　to　be　judged　from　their　results；　and　particularly　from　their　final　issue！　And　that　issue；　which　in　the　case　of　productive　knowledge　is　the　product；　in　the　knowledge　of　nature　is　the　unimpeachable　evidence　of　the　senses　as　to　each　fact。　　　The　result　of　their　view　is　that　earth　has　the　best　right　to　the　name　element；　and　is　alone　indestructible；　for　that　which　is　indissoluble　is　indestructible　and　elementary；　and　earth　alone　cannot　be　dissolved　into　any　body　but　itself。　Again；　in　the　case　of　those　elements　which　do　suffer　dissolution；　the　'suspension'　of　the　triangles　is　unsatisfactory。　But　this　takes　place　whenever　one　is　dissolved　into　another；　because　of　the　numerical　inequality　of　the　triangles　which　compose　them。　Further；　those　who　hold　these　views　must　needs　suppose　that　generation　does　not　start　from　a　body。　For　what　is　generated　out　of　planes　cannot　be　said　to　have　been　generated　from　a　body。　And　they　must　also　assert　that　not　all　bodies　are　divisible；　coming　thus　into　conflict　with　our　most　accurate　sciences；　namely　the　mathematical；　which　assume　that　even　the　intelligible　is　divisible；　while　they；　in　their　anxiety　to　save　their　hypothesis；　cannot　even　admit　this　of　every　perceptible　thing。　For　any　one　who　gives　each　element　a　shape　of　its　own；　and　makes　this　the　ground　of　distinction　between　the　substances；　has　to　attribute　to　them　indivisibility；　since　division　of　a　pyramid　or　a　sphere　must　leave　somewhere　at　least　a　residue　which　is　not　sphere　or　a　pyramid。　Either；　then；　a　part　of　fire　is　not　fire；　so　that　there　is　a　body　prior　to　the　element…for　every　body　is　either　an　element　or　composed　of　elements…or　not　every　body　is　divisible。
  8
  In　general；　the　attempt　to　give　a　shape　to　each　of　the　simple　bodies　is　unsound；　for　the　reason；　first；　that　they　will　not　succeed　in　filling　the　whole。　It　is　agreed　that　there　are　only　three　plane　figures　which　can　fill　a　space；　the　triangle；　the　square；　and　the　hexagon；　and　only　two　solids；　the　pyramid　and　the　cube。　But　the　theory　needs　more　than　these　because　the　elements　which　it　recognizes　are　more　in　number。　Secondly；　it　is　manifest　that　the　simple　bodies　are　often　given　a　shape　by　the　place　in　which　they　are　included；　particularly　water　and　air。　In　such　a　case　the　shape　of　the　element　cannot　persist；　for；　if　it　did；　the　contained　mass　would　not　be　in　continuous　contact　with　the　containing　body；　while；　if　its　shape　is　changed；　it　will　cease　to　be　water；　since　the　distinctive　quality　is　shape。　Clearly；　then；　their　shapes　are　not　fixed。　Indeed；　nature　itself　seems　to　offer　corroboration　of　this　theoretical　conclusion。　Just　as　in　other　cases　the　substratum　must　be　formless　and　unshapen…for　thus　the　'all…receptive'；　as　we　read　in　the　Timaeus；　will　be　best　for　modelling…so　the　elements　should　be　conceived　as　a　material　for　composite　things；　and　that　is　why　they　can　put　off　their　qualitative　distinctions　and　pass　into　one　another。　Further；　how　can　they　account　for　the　generation　of　flesh　and　bone　or　any　other　continuous　body？　The　elements　alone　cannot　produce　them　because　their　collocation　cannot　produce　a　continuum。　Nor　can　the　composition　of　planes；　for　this　produces　the　elements　themselves；　not　bodies　made　up　of　them。　Any　one　then　who　insists　upon　an　exact　statement　of　this　kind　of　theory；　instead　of　assenting　after　a　passing　glance　at　it；　will　see　that　it　removes　generation　from　the　world。　　　Further；　the　very　properties；　powers；　and　motions；　to　which　they　paid　particular　attention　in　allotting　shapes；　show　the　shapes　not　to　be　in　accord　with　the　bodies。　Because　fire　is　mobile　and　productive　of　heat　and　combustion；　some　made　it　a　sphere；　others　a　pyramid。　These　shapes；　they　thought；　were　the　most　mobile　because　they　offer　the　fewest　points　of　contact　and　are　the　least　stable　of　any；　they　were　also　the　most　apt　to　produce　warmth　and　combustion；　because　the　one　is　angular　throughout　while　the　other　has　the　most　acute　angles；　and　the　angles；　they　say；　produce　warmth　and　combustion。　Now；　in　the　first　place；　with　regard　to　movement　both　are　in　error。　These　may　be　the　figures　best　adapted　to　movement；　they　are　not；　however；　well　adapted　to　the　movement　of　fire；　which　is　an　upward　and　rectilinear　movement；　but　rather　to　that　form　of　circular　movement　which　we　call　rolling。　Earth；　again；　they　call　a　cube　because　it　is　stable　and　at　rest。　But　it　rests　only　in　its　own　place；　not　anywhere；　from　any　other　it　moves　if　nothing　hinders；　and　fire　and　the　other　bodies　do　the　same。　The　obvious　inference；　therefore；　is　that　fire　and　each　several　element　is　in　a　foreign　place　a　sphere　or　a　pyramid；　but　in　its　own　a　cube。　Again；　if　the　possession　of　angles　makes　a　body　produce　heat　and　combustion；　every　element　produces　heat；　though　one　may　do　so　more　than　another。　For　they　all　possess　angles；　the　octahedron　and　dodecahedron　as　well　as　the　pyramid；　and　Democritus　makes　even　the　sphere　a　kind　of　angle；　which　cuts　things　because　of　its　mobility。　The　difference；　then；　will　be　one　of　degree：　and　this　is　plainly　false。　They　must　also　accept　the　inference　that　the　mathematical　produce　heat　and　combustion；　since　they　to