criminal psychology-第38章

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s　it　is　to　be　expected　that　the　footprint　will　lead　to　results''　then　I　have　declared；　‘‘According　to　the　conditions　the　conditioned　probability　of　a　positive　result　is　great。''　Both　assertions　may　be　correct；　but　it　would　be　false　to　unite　them　and　to　say；　‘‘The　conditions　for　results　are　very　favorable　in　the　case　before　us；　but　generally　hardly　anything　is　gained　by　means　of　footprints；　and　hence　the　probability　in　this　case　is　small。''　This　would　be　false　because　the　few　favorable　results　as　against　the　many　unfavorable　ones　have　already　been　considered；　and　have　already　determined　the　percentage；　so　that　they　should　not　again　be　used。

Such　mistakes　are　made　particularly　when　determining　the　complicity　of　the　accused。　Suppose　we　say　that　the　manner　of　the　crime　makes　it　highly　probable　that　the　criminal　should　be　a　skilful；　frequently…punished　thief；　i。　e。；　our　probability　is　conditioned。　Now　we　proceed　to　unconditioned　probability　by　saying：　‘‘It　is　a　well…known　fact　that　frequently…punished　thieves　often　steal　again；　and　we　have　therefore　two　reasons　for　the　assumption　that　X；　of　whom　both　circumstances　are　true；　was　the　criminal。''　But　as　a　matter　of　fact　we　are　dealing　with　only　one　identical　probability　which　has　merely　been　counted　in　two　ways。　Such　inferences　are　not　altogether　dangerous　because　their　incorrectness　is　open　to　view；　but　where　they　are　more　concealed　great　harm　may　be　done　in　this　way。

A　further　subdivision　of　probability　is　made　by　Kirchmann。＇1＇　He　distinguished：


＇1＇　ber　die　Wahrscheinlicbkeit；　Leipzig　1875。


（1）　General　probability；　which　depends　upon　the　causes　or　consequences　of　some　single　uncertain　result；　and　derives　its　character　from　them。　An　example　of　the　dependence　on　causes　is　the　collective　weather　prophecy；　and　of　dependence　on　consequences　is　Aristotle's　dictum；　that　because　we　see　the　stars　turn　the　earth　must　stand　still。　Two　sciences　especially　depend　upon　such　probabilities：　history　and　law；　more　properly　the　practice　and　use　of　criminal　　law。　Information　imparted　by　men　is　used　in　both　sciences；　this　information　is　made　up　of　effects　and　hence　the　occurrence　is　inferred　from　as　cause。

（2）　Inductive　probability。　Single　events　which　must　be　true；　form　the　foundation；　and　the　result　passes　to　a　valid　universal。　（Especially　made　use　of　in　the　natural　sciences；　e。　g。；　in　diseases　caused　by　bacilli；　in　case　X　we　find　the　appearance　A　and　in　diseases　of　like　cause　Y　and　Z；　we　also　find　the　appearance　A。　It　is　therefore　probable　that　all　diseases　caused　by　bacilli　will　manifest　the　symptom　A。）

（3）　Mathematical　Probability。　This　infers　that　A　is　connected　either　with　B　or　C　or　D；　and　asks　the　degree　of　probability。　I。　e。：　A　woman　is　brought　to　bed　either　with　a　boy　or　a　girl：　therefore　the　probability　that　a　boy　will　be　born　is　one…half。

Of　these　forms　of　probability　the　first　two　are　of　equal　importance　to　us；　the　third　rarely　of　value；　because　we　lack　arithmetical　cases　and　because　probability　of　that　kind　is　only　of　transitory　worth　and　has　always　to　be　so　studied　as　to　lead　to　an　actual　counting　of　cases。　It　is　of　this　form　of　probability　that　Mill　advises　to　know；　before　applying　a　calculation　of　probability；　the　necessary　facts；　i。　e。；　the　relative　frequency　with　which　the　various　events　occur；　and　to　understand　clearly　the　causes　of　these　events。　If　statistical　tables　show　that　five　of　every　hundred　men　reach；　on　an　average；　seventy　years；　the　inference　is　valid　because　it　expresses　the　existent　relation　between　the　causes　which　prolong　or　shorten　life。

A　further　comparatively　self…evident　division　is　made　by　Cournot；　who　separates　subjective　probability　from　the　possible　probability　pertaining　to　the　events　as　such。　The　latter　is　objectively　defined　by　Kries＇1＇　in　the　following　example：


＇1＇　J。　v。　Kries：　ber　die　Wahrseheinlichkeit　Il。　Mglichkeit　u。　ihre　Bedeutung　in　Strafrecht。　Zeitschrift　f。　d。　ges。　St。　R。　W。　Vol。　IX；　1889。


‘‘The　throw　of　a　regular　die　will　reveal；　in　the　great　majority　of　cases；　the　same　relation；　and　that　will　lead　the　mind　to　suppose　it　objectively　valid。　It　hence　follows；　that　the　relation　is　changed　if　the　shape　of　the　die　is　changed。''　But　how　‘‘this　objectively　valid　relation；''　i。　e。；　substantiation　of　probability；　is　to　be　thought　of；　remains　as　unclear　as　the　regular　results　of　statistics　do　anyway。　It　is　hence　a　question　whether　anything　is　gained　when　the　form　of　calculation　is　known。

Kries　says；　‘‘Mathematicians；　in　determining　the　laws　of　probability；　have　subordinated　every　series　of　similar　cases　which　take　　one　course　or　another　as　if　the　constancy　of　general　conditions；　the　independence　and　chance　equivalence　of　single　events；　were　identical　throughout。　Hence；　we　find　there　are　certain　simple　rules　according　to　which　the　probability　of　a　case　may　be　calculated　from　the　number　of　successes　in　cases　observed　until　this　one　and　from　which；　therefore；　the　probability　for　the　appearance　of　all　similar　cases　may　be　derived。　These　rules　are　established　without　any　exception　whatever。''　This　statement　is　not　inaccurate　because　the　general　applicability　of　the　rules　is　brought　forward　and　its　use　defended　in　cases　where　the　presuppositions　do　not　agree。　Hence；　there　are　delusory　results；　e。　g。；　in　the　calculation　of　mortality；　of　the　statements　of　witnesses　and　judicial　deliverances。　These　do　not　proceed　according　to　the　schema　of　the　ordinary　play　of　accident。　The　application；　therefore；　can　be　valid　only　if　the　constancy　of　general　conditions　may　be　reliably　assumed。

But　this　evidently　is　valid　only　with　regard　to　unconditioned　probability　which　only　at　great　intervals　and　transiently　may　influence　our　practical　work。　For；　however　well　I　may　know　that　according　to　statistics　every　xth　witness　is　punished　for　perjury；　I　will　not　be　frightened　at　the　approach　of　my　xth　witness　though　he　is　likely；　according　to　statistics；　to　lie。　In　such　cases　we　are　not　fooled；　but　where　events　are　confused　we　still　are　likely　to　forget　that　probabilities　may　be　counted　only　from　great　series　of　figures　in　which　the　experiences　of　individuals　are　quite　lost。

Nevertheless　figures　and　the　conditions　of　figures　with　regard　to　probability　exercise　great　influence　upon　everybody；　so　great　indeed；　that　we　really　must　beware　of　going　too　far　in　the　use　of　figures。　Mill　cites　a　case　of　a　wounded　Frenchman。　Suppose　a　regiment　made　up　of　999　Englishmen　and　one　Frenchman　is　attacked　and　one　man　is　wounded。　No　one　would　believe　the　account　that　this　one　Frenchman　was　the　one　wounded。　Kant　says　significantly：　‘‘If　anybody　sends　his　doctor　9　ducats　by　his　servant；　the　doctor　certainly　supposes　that　the　servant　has　either　lost　or　otherwise　disposed　of　one　ducat。''　These　are　merely　probabilities　which　depend　upon　habits。　So；　it　may　be　supposed　that　a　handkerchief　has　been　lost　if　only　eleven　are　found；　or　people　may　wonder　at　the　doctor's　ordering　a　tablespoonful　every　five　quarters　of　an　hour；　or　if　a　job　is　announced　with　2437　a　year　as　salary。

But　just　as　we　presuppose　that　wherever　the　human　will　played　any　part；　regular　forms　will　come　to　light；　so　we　begin　to　doubt　that　such　forms　will　occur　where　we　find　that　accident；　natural　　law；　or　the　unplanned　coperation　of　men　were　determining　factors；　If　I　permit　anybody　to　count　up　accidentally　concurrent　things　and　he　announces　that　their　number　is　one　hundred；　I　shall　probably　have　him　count　over　again。　I　shall　be　surprised　to　hear　that　somebody's　collection　contains　exactly　1000　pieces；　and　when　any　one　cites　a　distance　of　300　steps　I　will　suppose　that　he　had　made　an　approximate　estimation　but　had　not　counted　the　steps。　This　fact　is　well　known　to　people　who　do　not　care　about　accuracy；　or　who　want　to　give　their　statements　the　greatest　possible　appearance　of　correctness；　hence；　in　citing　figures；　they　make　use　of　especially　irregular　numbers；　e。　g。　1739；　；　3。25％；　etc。　I　know　a　case　of　a　vote　of　jurymen　in　which　even　the　proportion　of　votes　had　to　be　rendered　probable。　The　same　jury　had　to　pass　that　day　on　three　small　cases。　In　the　first　case　the　proportion　was　8　for；　4　against；　the　second　case　showed　the　same　proportion　and　the　third　case　the　same。　But　when　the　foreman　observed　the　proportion　he　announced　that　one　juryman　must　change　his　vote　because　the　same　proportion　three　times　running　would　appear　too　improbable！　If　we　want　to　know　the　reason　for　our　superior　trust　in　irregularity　in　such　cases；　it　is　to　be　found　in　the　fact　that　experience　shows　nature；　in　spite　of　all　her　marvelous　orderliness　in　the　large；　to　be　completely　free；　and　hence　irregular　in　little　things。　Hence；　as　Mill　shows　in　more　detail；　we　expect　no　identity　of　form　in　nature。　We　do　not　expect　next　year　to　have　the　same　order　of　days　as　this　year；　and　we　never　wonder　when　some　suggestive　regularity　is　broken　by　a　new　event。　Once　it　was　supposed　that　all　men　were　either　black　or　white；　and　then　red　men　were　discovered　in　America。　Now　just　exactly　such　suppositions　cause　the　greatest　difficulties；　because　we　do　not　know　the　limits　of　natural　law。　For　example；　we　do　not　doubt　that　all　bodies　on　earth　have　weight。　And　we　expect　to　find　no　exception　to　this　rule　on　reaching　some　undiscovered　island　on　our　planet；　all　bodies　will　have　weight　there　as　well　as　everywhere　else。　But　the　possibility　of　the　existence　of　red　men　had　to　be　granted　even　before　the　discovery　of　America。　Now　where　is　the　difference　between　the　propositions：　All　bodies　have　weight；　and；　All　men　are　either　white　or　black？　It　may　be　said　circularly　the　first　is　a　natural　law　and　the　second　is　not。　But　why　not？　Might　not　the　human　body　be　so　organized　that　according　to　the　natural　law　it　would　be　impossible　for　red　men　to　exist？　And　what　accurate　knowledge　have　we　of　pigmentation？　Has　anybody　ever　seen　a　green　horse？　And　is　the　accident　that　nobody　has　ever　seen　one　to　prevent　the　　discovery　of　green　horses　in　the　heart　of　Africa？　May；　perhaps；　somebody　not　breed　green　horses　by　crossings　or　other　experiments？　Or　is　the　existence　of　green　horses　contrary　to　some　unknown　but　invincible　natural　law？　Perhaps　somebody　may　have　a　green　horse　to…morrow；　perhaps　it　is　as　impossible　as　water　running　up　hill。

To　know　whether　anything　is　natural　law　or　not　always　depends　upon　the　grade　and　standing　of　our　immediate　experienceand　hence　we　shall　never　be　able　honestly　to　make　any　universal　proposition。　The　only　thing　possible　is　the　greatest　possible　accurate　observation　of　probability　in　all　known　possible　cases；　and　of　the　probability　of　the　discovery　of　exceptions。　Bacon　called　the　establishment　of　reliable　assumptions；　counting　up　without　meeting　any　contradictory　case。　But　what　gives　us　the　law　is　the　manner　of　counting。　The　untrained　mind　accepts　facts　as　they　occur　without　taking　the　trouble　to　seek　others；　the　trained　mind　seeks　the　facts　he　needs　for　the　premises　of　his　inference。　As　Mill　says；　whatever　has　shown　itself　to　be　true　without　exception　may　be　held　universal　so　long　as　no　doubtful　exception　is　presented；　and　when　the　case　is　of　such　a　nature　that　a　real　exception　could　not　escape　our　observation。

This　indicates　how　we　are　to　interpret　information　given　by　others。　We　hear；　‘‘Inasmuch　as　this　is　always　so　it　ma