other　that　of　things　which　relate　to　what　is　extended。”　Thought；　the　Notion；　the　spiritual；　the
  self…conscious；　is　what　is　at　home　with　itself；　and　its　opposite　is　contained　in　what　is　extended；
  spatial；　separated；　not　at　home　with　itself　nor　free。　This　is　the　real　distinction　（distinctio　realis）　of
  substances：　“The　one　substance　can　be　clearly　and　definitely　comprehended　without　the　other。　But
  the　corporeal　and　the　thinking　and　creating　substance　can　be　comprehended　under　this　common
  notion；　for　the　reason　that　they　are　things　which　require　God’s　support　alone　in　order　to　exist。”
  They　are　universal；　other　finite　things　require　other　things　as　conditions　essential　to　their　existence。
  But　extended　substance；　the　kingdom　of　nature；　and　spiritual　substance；　do　not　require　one
  another。　They　may　be　called　substances；　because　each　of　them　constitutes　an　entire　range　or
  sphere；　an　independent　totality。　But　because；　Spinoza　concluded；　each　side；　the　kingdom　of
  thought　as　well　as　nature；　is　one　complete　system　within　itself；　they　are　likewise　in　themselves；　that
  is　absolutely；　identical　as　God；　the　absolute　substance；　for　thinking　spirit　this　implicit　is　thus　God；
  or　their　differences　are　ideal。
  Descartes　proceeds　from　the　Notion　of　God　to　what　is　created；　to　thought　and　extension；　and
  from　this　to　the　particular。　“Now　substances　have　several　attributes　without　which　they　cannot　be
  thought〃　—　that　signifies　their　determinateness　—　〃but　each　has　something　peculiar　to　itself　which
  constitutes　its　nature　and　essence〃　—　a　simple　universal　determinateness　—　〃and　to　which　the
  others　all　relate。　Thus　thought；　constitutes　the　absolute　attribute　of　mind；”　thought　is　its　quality；
  “extension　is〃　the　essential　determination　of　corporeality；　and　this　alone　is　“the　true　nature　of
  body。　What　remains　are　merely　secondary　qualities；　modes；　like　figure　and　movement　in　what　is
  extended；　imagination；　feeling　and　will　in　thinking；　they　may　be　taken　away　or　thought　away。　God
  is　the　uncreated；　thinking　substance。”　（30）
  Descartes　here　passes　to　what　is　individual；　and　because　he　follows　up　extension　he　arrives　at
  matter；　rest；　movement。　One　of　Descartes’　main　points　is　that　matter；　extension；　corporeality；　are
  quite　the　same　thing　for　thought；　according　to　him　the　nature　of　body　is　fulfilled　in　its　extension；　and
  this　should　be　accepted　as　the　only　essential　fact　respecting　the　corporeal　world。　We　say　that
  body　offers　resistance；　has　smell；　taste；　colour；　transparency；　hardness；　&c。；　since　without　these
  we　can　have　no　body。　All　these　further　determinations　respecting　what　is　extended；　such　as　size；
  rest；　movement；　and　inertia；　are；　however；　merely　sensuous；　and　this　Descartes　showed；　as　it　had
  long　before　this　been　shown　by　the　Sceptics。　Undoubtedly　that　is　the　abstract　Notion　or　pure
  essence；　but　to　body　or　to　pure　existence；　there　likewise　of　necessity　pertains　negativity　or
  diversity。　By　means　of　the　following　illustration　Descartes　showed　that　with　the　exception　of
  extension；　all　corporeal　determinations　may　be　annihilated；　and　that　none　can　be　absolutely
  predicated。　We　draw　conclusions　respecting　the　solidity　and　hardness　of　matter　from　the
  resistance　which　a　body　offers　to　our　disturbance；　and　by　means　of　which　it　seeks　to　hold　its
  place。　Now　if　we　admit　that　matter　as　we　touch　it　always　gives　way　to　as　like　space；　we　should
  have　no　reason　for　ascribing　to　it　solidity。　Smell；　colour；　taste；　are　in　the　same　way　sensuous
  qualities　merely；　but　what　we　clearly　perceive　is　alone　true。　If　a　body　is　ground　into　small　parts；　it
  gives　way；　and　yet　it　does　not　lose　its　nature；　resistance　is　thus　not　essential。（31）　This
  not…being…for…itself　is　however　a　quantitatively　slighter　resistance　only；　the　resistance　always
  remains。　But　Descartes　desires　only　to　think；　now　he　does　not　think　resistance；　colour；　&c。；　but
  apprehends　them　by　the　senses　only。　Hence　he　says　that　all　this　must　be　led　back　to　extension　as
  being　special　modifications　of　the　same。　It　is　undoubtedly　to　the　credit　of　Descartes　that　he　only
  accepts　as　true　what　is　thought；　but　the　abrogation　of　these　sensuous　qualities　simply　represents
  the　negative　movement　of　thought：　the　essence　of　body　is　conditioned　through　this　thought；　that　is；
  it　is　not　true　essence。
  Descartes　now　makes　his　way　from　the　Notion　of　extension　to　the　laws　of　motion；　as　the　universal
  knowledge　of　the　corporeal　in　its　implicitude；　he　shows　that　there　is　no　vacuum；　for　that　would　be
  an　extension　without　bodily　substance；　i。e。　a　body　without　body；　that　there　are　no　atoms　（no
  indivisible　independent　existence）；　for　the　same　reason；　viz。；　because　the　essence　of　body　is
  extension。　He　further　shows　that　a　body　is　set　in　motion　by　something　outside　of　it；　but　of　itself　it
  continues　in　a　condition　of　rest；　and　likewise　it　must；　when　in　a　condition　of　movement；　be　brought
  to　rest　by　another　outside　of　it　—　this　is　the　property　of　inertia。（32）　These　are　unmeaning
  propositions；　for　an　abstraction　is　involved　for　instance　in　asserting　simple　rest　and　movement　in
  their　opposition。
  Extension　and　motion　are　the　fundamental　conceptions　in　mechanical　physics；　they　represent　the
  truth　of　the　corporeal　world。　It　is　thus　that　ideality　comes　before　the　mind　of　Descartes；　and　he　is
  far　elevated　above　the　reality　of　the　sensuous　qualities；　although　he　does　not　reach　so　far　as　to　the
  separation　of　this　ideality。　He　thus　remains　at　the　point　of　view　of　mechanism　pure　and　simple。
  Give　me　matter　（extension）　and　motion　and　I　will　build　worlds　for　you；　is　what　Descartes　virtually
  says。（33）　Space　and　time　were　hence　to　him　the　only　determinations　of　the　material　universe。　In
  this；　then；　lies　the　mechanical　fashion　of　viewing　nature；　or　the　natural　philosophy　of　Descartes　is
  seen　to　be　purely　mechanical。（34）　Hence　changes　in　matter　are　due　merely　to　motion；　so　that
  Descartes　traces　every　relationship　to　the　rest　and　movement　of　particles；　and　all　material　diversity
  such　as　colour；　and　taste　—　in　short；　all　bodily　qualities　and　animal　phenomena　—　to　mechanism。　In
  living　beings　processes　such　as　that　of　digestion　are　mechanical　effects　which　have　as　principles；
  rest　and　movement。　We　here　see　the　ground　and　origin　of　the　mechanical　philosophy；　but　further
  on　we　find　that　this　is　unsatisfactory；　for　matter　and　motion　do　not　suffice　to　explain　life。　Yet　the
  great　matter　in　all　this　is　that　thought　goes　forward　in　its　determinations；　and　that　it　constitutes　from
  these　thought…determinations　the　truth　of　nature。
  In　his　consideration　of　the　system　of　the　world　and　the　movement　of　the　heavenly　bodies；
  Descartes　has　worked　out　the　mechanical　view　more　fully。　He　thus　comes　to　speak　of　the　earth；
  the　sun；　&c。；　and　of　his　conception　of　the　circling　motion　of　the　heavenly　bodies　in　the　form　of
  vortices：　of　metaphysical　hypotheses　as　to　how　small　particles　pass　into；　out　of；　and　through　pores
  and　act　on　one　another；　and　finally　to　saltpetre　and　gunpowder。（35）
  Universal　reflections　should　have　the　first　claim　on　our　attention；　but　on　the　other　hand　the
  transition　to　the　determinate　is　accomplished　in　a　system　of　Physics　which　is　the　result　of
  observations　and　experiences；　and　this　is　done　entirely　by　means　of　the　understanding。　Descartes
  thus　mingles　many　observations　with　a　metaphysic　of　this　nature；　and　to　us　the　result　is　hence
  obscure。　In　this　philosophy　the　thinking　treatment　of　empiricism　is　thus　predominant；　and　a　similar
  method　has　been　adopted　by　philosophers　from　this　time　on。　To　Descartes　and　others；　Philosophy
  had　still　the　more　indefinite　significance　of　arriving　at　knowledge　through　thought；　reflection；　and
  reasoning。　Speculative　cognition；　the　derivation　from　the　Notion；　the　free　independent
  development　of　the　matter　itself；　was　first　introduced　by　Fichte；　and　consequently　what　is　now
  called　philosophic　knowledge　is　not　yet　separated　in　Descartes　from　the　rest　of　scientific
  knowledge。　In　those　times　all　the　knowledge　of　mankind　was　called　philosophy；　in　Descartes’
  metaphysics　we　thus　saw　quite　empirical　reflection　and　reasoning　from　particular　grounds；　from
  experiences；　facts；　phenomena；　being　brought　into　play　in　the　na？vest　manner；　and　one　has　no
  sense　of　speculation　in　the　matter。　The　strictly　scientific　element　here　really　consisted　mainly　in　the
  method　of　proof　as　it　has　long　been　made　use　of　in　geometry；　and　in　the　ordinary　method　of　the
  formal　logical　syllogism。　Hence　it　likewise　happens　that　Philosophy；　which　ought　to　form　a　totality
  of　the　sciences；　begins　with　logic　and　metaphysics；　the　second　part　is　composed　of　ordinary
  physics　and　mathematics；　mingled　no　doubt　with　metaphysical　speculations；　and　the　third　part；
  ethics；　deals　with　the　nature　of　man；　his　duties；　the　state；　the　citizen。　And　this　is　the　case　with
  Descartes。　The　first　part　of　the　Principia　philosophi？　treats　De　principiis　cognitionis　human？；
  the　second　De　principiis　rerum　materialium。　This　natural　philosophy；　as　a　philosophy　of
  extension；　is；　however；　none　other　than　what　a　quite　ordinary　physics　or　mechanics　might　at　that
  time　be；　and　it　is　still　quite　hypothetical；　we；　on　the　other　hand；　accurately　distinguish　empirical
  physics　and　natural　philosophy；　first　likewise　pertains