criminal psychology-第52章
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ften 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 undiscovere
