ience of criminal law demands the observation of the facts of the daily life_。 In this observation consists the alpha and omega of our work； we can perform it only with the flux of sensory appearances； and the law which determines this flux； and according to which the appearances come； is the law of causation。 But we are nowhere so neglectful of causation as in the deeds of mankind。 A knowledge of that region only psychology can give us。 Hence； to become conversant with psychological principles； is the obvious duty of that conscientiousness which must hold first place among the forces that conserve the state。 It is a fact that there has been in this matter much delinquency and much neglect。 If； then； we were compelled to endure some bitterness on account of it； let it be remembered that it was always directed upon the fact that we insisted on studying our statutes and their commentaries； fearfully excluding every other discipline that might have assisted us； and have imported vitality into our profession。 It was Gneist＇1＇ who complained： ‘‘The contemporary low stage of legal education is to be explained like much else by that historical continuity which plays the foremost rle in the administration of justice。'' Menger＇2＇ does not mention ‘‘historical continuity'' so plainly； but he points sternly enough to the legal sciences as the most backward of all disciplines that were in contact with contemporary tendencies。 That these accusations are justified we must admit； when we consider what Stlzel＇3＇ and the genial creator of modern civil teaching demands： ‘‘It must be recognized that jurisprudence in reality is nothing but the thesis of the healthy human understanding in matters of law。'' But what the ‘‘healthy human mind'' requires we can no longer discover from our statutory paragraphs only。 How shameful it is for us； when Goldschmidt＇4＇ openly narrates how a famous scientist exclaimed to a student in his laboratory： ‘‘What do you want here？ You know nothing； you understand nothing； you do nothing；you had better become a lawyer。''
＇1＇ R。 Gneist： Aphorismen zur Reform des Rechtestudiums。 Berlin 1887。
＇2＇ A。 Menger： in Archiv fin soziale Gesetzgebung v。 Braun II。
＇3＇ A。 Stlsel： Schulung fin die Zivilistiche Praxis。 2d Ed。 Berlin 1896。
＇4＇ S。 Goldschmidt： Rechtestudium und Priifungsordnung。 Stuttgart 1887。
Now let us for once frankly confess why we are dealt these disgraceful reproaches。 Let us agree that we have not studied or dealt with jurisprudence as a science； have never envisaged it as an empirical discipline； that the aprioristic and classical tradition had kept this insight at a distance； and that where investigation and effort toward the recognition of the true is lacking； there lacks everything of the least scientific importance。 To be scientifically legitimate； we need first of all the installation of the disciplines of research which shall have direct relationships with our proper task。 In this way only can we attain that spiritual independence by means of spiritual freedom； which Goldschmidt defines as the affair of the higher institutions of learning； and which is also the ideal of our own business in life。 And this task is not too great。 ‘‘Life is movement；'' cried Alois von Brinz；＇1＇ in his magnificent inaugural address。 ‘‘Life is not the thought； but the thinking which comes in the fullness of action。''
It may be announced with joy and satisfaction； that since the publication of the first edition of this book； and bearing upon it； there came to life a rich collection of fortuitous works which have brought together valuable material。 Concerning the testimony of witnesses； its nature and value； concerning memory； and the types of reproduction； there is now a considerable literature。 Everywhere industrious hands are raised；hands of psychologists； physicians； and lawyers； to share in the work。 Should they go on unhurt we may perhaps repair the unhappy faults committed by our ancestors through stupid ignorance and destructive use of uncritically collected material。
＇1＇ A。 v。 Brinz： ber Universalitt。 Rektorsrede 1876。
PART I。
THE SUBJECTIVE CONDITIONS OF EVIDENCE： THE MENTAL ACTIVITIES OF THE JUDGE。
TITLE A。 THE CONDITIONS OF TAKING EVIDENCE。
Topic I。 METHOD。
Section I。 （a） General Considerations。
SOCRATES； dealing in the Meno with the teachability of virtue； sends for one of Meno's slaves； to prove by him the possibility of absolutely certain a priori knowledge。 The slave is to determine the length of a rectangle； the contents of which is twice that of one measuring two feet； but he is to have no previous knowledge of the matter； and is not to be directly coached by Socrates。 He is to discover the answer for himself。 Actually the slave first gives out an incorrect answer。 He answers that the length of a rectangle having twice the area of the one mentioned is four feet； thinking that the length doubles with the area。 Thereupon Socrates triumphantly points out to Meno that the slave does as a matter of fact not yet quite know the truth under consideration； but that he really thinks he knows it； and then Socrates； in his own Socratic way； leads the slave to the correct solution。 This very significant procedure of the philosopher is cited by Guggenheim＇1＇ as an illustration of the essence of a priori knowledge； and when we properly consider what we have to do with a witness who has to relate any fact； we may see in the Socratic method the simplest example of our task。 We must never forget _that the majority of mankind dealing with any subject whatever always believe that they know and repeat the truth_； and even when they say doubtfully： ‘‘I believe。 It seems to me；'' there is； in this tentativeness； more meant than meets the ear。 When anybody says： ‘‘I believe that'' it merely means that he intends to insure himself against the event of being contradicted by better informed persons； but he certainly has not
＇1＇ M。 Guggenheim： Die Lehre vom aprioristischen Wissen。 Berlin 1885。
the doubt his expression indicates。 When； however； the report of some bare fact is in question （‘‘It rained；'' ‘‘It was 9 o'clock；'' ‘‘His beard was brown；'' or ‘‘It was 8 o'clock；''） it does not matter to the narrator； and if he imparts _*such_ facts with the introduction； ‘‘I believe；'' then he was really uncertain。 The matter becomes important only where the issue involves partly…concealed observations； conclusions and judgments。 In such cases another factor entersconceit； what the witness asserts he is fairly certain of just because he asserts it； and all the ‘‘I believes；'' ‘‘Perhapses；'' and ‘‘It seemeds；'' are merely insurance against all accidents。
Generally statements are made without such reservations and； even if the matter is not long certain； with full assurance。 What thus holds of the daily life； holds also； and more intensely； of court… witnesses； particularly in crucial matters。 Anybody experienced in their conduct comes to be absolutely convinced that witnesses do not know what they know。 A series of assertions are made with utter certainty。 Yet when these are successively subjected to closer examinations； tested for their ground and source； only a very small portion can be retained unaltered。 Of course； one may here overshoot the mark。 It often happens； even in the routine of daily life； that a man may be made to feel shaky in his most absolute convictions； by means of an energetic attack and searching questions。 Conscientious and sanguine people are particularly easy subjects of such doubts。 Somebody narrates an event； questioning begins as to the indubitability of the fact； as to the exclusion of possible deception； the narrator becomes uncertain； he recalls that； because of a lively imagination； he has already believed himself to have seen things otherwise than they actually were； and finally he admits that the matter might probably have been different。 During trials this is still more frequent。 The circumstance of being in court of itself excites most people； the consciousness that one's statement is； or may be； of great significance increases the excitement； and the authoritative character of the official subdues very many people to conform their opinions to his。 What wonder then； that however much a man may be convinced of the correctness of his evidence； he may yet fail in the face of the doubting judge to know anything certainly？
Now one of the most difficult tasks of the criminalist is to hit； in just such cases； upon the truth； neither to accept the testimony blindly and uncritically； nor to render the witness； who otherwise is telling the truth； vacillating and doubtful。 But it is still more difficult to lead the witness； who is not intentionally falsifying； but has merely observed incorrectly or has made false conclusions； to a statement of the truth as Socrates leads the slave in the Meno。 It is as modern as it is comfortable to assert that this is not the judge's businessthat the witness is to depose； his evidence is to be accepted； and the judge is to judge。 Yet it is supposed before everything else that the duty of the court is to establish the material truththat the formal truth is insufficient。 Moreover； if we notice false observations and let them by； then； under certain circumstance； we are minus one important piece of evidence _*pro_ and _*con_； and the whole case may be turned topsy turvy。 At the very least a basis of development in the presentation of evidence is so excluded。 We shall； then； proceed in the Socratic fashion。 But； inasmuch as we are not concerned with mathematics； and are hence more badly placed in the matter of proof； we shall have to proceed more cautiously and with less certainty； than when the question is merely one of the area of a square。 On the one hand we know only in the rarest cases that we are not ourselves mistaken； so that we must not； without anything further； lead another to agree with us； on the other hand we must beware of perverting the witness from his possibly sound opinions。 It is not desirable to speak of suggestion in this matter； since； if I believe that the other fellow knows a matter better than I and conform to his opinion； there is as yet no suggestion。 And this pure form of change of