criminal psychology-第41节
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own work； we must consider that the progress of knowledge consists in the collection of instances； and anything that might have been normal in 100 cases； need not in any sense be so when 1000 cases are in question。 Yesterday the norm may have been subject to no exception； to…day exceptions are noted； and to…morrow the exception has become the rule。
Hence； rules which have no exceptions grow progressively rarer； and wherever a single exception is discovered the rule can no longer be held as normative。 Thus； before New Holland was discovered； all swans were supposed to be white； all mammals incapable of laying eggs； now we know that there are black swans and that the duck…bill lays eggs。 Who would have dared to assert before the discovery of the X…ray that light can penetrate wood； and who； especially； has dared to make generalizations with regard to the great inventions of our time which were not afterwards contradicted by the facts？ It may be that the time is not too far away in which great； tenable and unexceptionable principles may be posited； but the present tendency is to beware of generalizations； even so far as to regard it a sign of scientific insight when the composition of generally valid propositions is made with great caution。 In this regard the great physicians of our time are excellent examples。 They hold： ‘‘whether the phenomenon A is caused by B we do not know； but nobody has ever yet seen a case of A in which the precedence of B could not be demonstrated。'' Our experts should take the same attitude in most cases。 It might be more uncomfortable for us； but certainly will be safer； for if they do not take that attitude we are in duty bound to presuppose in our conclusions that they have taken it。 Only in this wise； by protecting ourselves against apparently exceptionless general rules； can our work be safely carried on。
This becomes especially our duty where； believing ourselves to have discovered some generally valid rule； we are compelled to draw conclusions without the assistance of experts。 How often have we depended upon our understanding and our ‘‘correct'' a priori method of inference； where that was only experience；and such poor experience！ We lawyers have not yet brought our science so far as to be able to make use of the experience of our comrades with material they have reviewed and defined in writing。 We have bothered a great deal about the exposition of some legal difficulty； the definition of some judicial concept； but we have received little instruction or tradition concerning mankind and its passions。 Hence； each one has to depend on his own experience； and that is supposed to be considerable if it has a score of years to its back； and is somewhat supplemented by the experience； of others。 In this regard there are no indubitable rules； everybody must tell himself； ‘‘I have perhaps never experienced this fact； but it may be that a thousand other people have seen it； and seen it in a thousand different ways。 How then； and whence； my right to exclude every exception？''
We must never forget that every rule is shattered whenever any single element of the situation is unknown； and that happens very easily and frequently。 Suppose that I did not have full knowledge of the nature of water； and walked on terra firma to the edge of some quiet； calm pool。 When now I presume： water has a body； it has a definite density； it has consistency； weight； etc。； I will also presume that I may go on walking over its surface just as over the surface of the earth；and that； simply because I am ignorant of its fluidity and its specific gravity。 Liebman＇1＇ summarizes the situation as follows。 The causal nexus； the existential and objective relation between lightning and thunder； the firing of powder and the explosion； are altogether different from the logical nexus； i。 e。 the mere conceptual connection between antecedent and consequent in deduction。 This constitutes the well known kernel of Humian skepticism。 We must keep in mind clearly that we never can know with certainty whether we are in possession of all the determining factors of a phenomenon； and hence we must adhere to the only unexceptionable rule： _Be careful about making rules that admit of no exceptions_。 There is still another objection to discuss； i。 e。 the mathematical exception to Humian skepticism。 It might be held that inasmuch as the science of justice is closely related in many ways to mathematics； it may permit of propositions a priori。 Leibnitz already had said； ‘‘The mathematicians count with numbers； the lawyers with ideas；fundamentally both do the same thing。'' If the relationship were really so close； general skepticism about phenomenal sciences could not be applied to the legal disciplines。 But we nowadays deal not with concepts merely； and in spite of all obstruction； Leibnitz's time has passed and the realities of our profession； indeed its most important object； the human being itself； constitute an integrating part of our studies。 And the question may be still further raised whether mathematics is really so exempt from skepticism。 The work of Gauss； Lobatschewski； Bolyai； Lambert； would make the answer negative。
＇1＇ Liebman Zur Analysis der Wirklichkeit。 Strassburg 1888。
Let us； for once； consider what significance mathematical postulates have。 When Pythagoras discovered his proposition in such a way that he first drew a right…angled triangle and then built a square on each of the sides； and finally measured the area of each and compared them； he must at first have got the notion that that also might be merely accidental。 If he had made the construction 10 or 100 times with various triangles and these had resulted always identically； only then might he have been justified in saying that he had apparently discovered a theorem。 But then his process was just as thoroughly experiential as that of a scientist who says that a bird has never yet been observed to give birth to living young； and that hence all birds lay eggs。
But Pythagoras did not proceed in this experiential manner in the discovery of his theorem。 He constructed and he counted； and when he did that he acted on postulates： ‘‘If this is a right…angled triangle and if that be a square； so；''and this is just what is done in every science。 The general propositions are； ‘‘If the relations remain the same as formerly the moon must rise to…morrow at such and such a time。'' ‘‘If this step in a deduction is not false； if it is well grounded at this point； if it really refers to x； it follows。。。。 '' In his procedures the criminalist does exactly the same thing。 What he must be skeptical about is the postulates from which he starts。
Section 26。 （d） The Empirical Method in the Study of Cases。
Properly to bound our discussion of Humian skepticism； a few words have to be said concerning the empirical method of the sciences。 We will call those laws purely empirical which； in the study of nature； yield regularities that are demonstrated by observation and experiment； but upon which little or no reliance is placed with regard to cases which differ considerably from the observed。 The latter is done because no reason is seen for the existence of such laws。 The empirical rule is； therefore； no final law； but is capable of explaining； especially when true； e。 g。； the succession of a certain condition of weather from certain meteorological signs； the improvement of species through crossing； the fact that some alloys are harder than their components； and so on。 Or； to choose examples from our own field； jurisprudence may assert as empirical law that a murderer is a criminal who has gone unpunished for his earlier crimes； that all gamblers show such significant resemblances； that the criminal who has soiled his hands with blood in some violent crime was accustomed to wipe them on the underside of a table； that the slyest person generally perpetrates some gross stupidity after committing a serious crime； and so renders discovery simpler； that lust and cruelty have a certain relation； that superstition plays a great rle in crime； etc。
It is of exceeding importance to establish such purely empiric laws in our science； which has done little with such matters because； owing to scanty research into most of them； we need these laws。 We know approximately that this and that have come to light so and so often； but we have not reduced to order and studied systematically the cases before us； and we dare not call this knowledge natural law because we have subjected it to no inductive procedure。 ‘‘The reference of any fact discovered by experience to general laws or rules we call induction。 It embraces both observation and deduction。'' Again； it may be defined as ‘‘the generalization or universalization of our experiences； and inference that a phenomenon occurring x times will invariably occur when the essential circumstances remain identical。 The earliest investigators started with the simplest inductions；that fire burns； that water flows downward；so that new； simple truths were continually discovered。 This is the type of scientific induction and it requires further； the addition of certainty and accuracy。''＇1＇
The foregoing might have been written expressly
