Chapter XXVII: Section 22

The study of the human soul as psychology, has for its subject the whole stream of conscious life and for its aim the discovery of the occurrence and relation of the laws of human thought. Now whether these relations imply the coherence of the objects thought about or not, so long as logic is dealing with the laws according to which thoughts must be correlated in order to attain to objectively valid knowledge, all questions that deal with the formal aspect of thinking do not enter the field of psychological investigation. The general psychological problem is to describe the actual psychic events as they occur, to analyze them into their simplest elements, and inasmuch as it is this purely pragmatic application of psychology to the problem of inference that concerns us, we need to deal only with that law which defines the combination of images and with the question,--how the spirit achieves this combination. The material aspect of this question is therefore psychological. The legal importance of the problem lies in the very potent fact that inferences and theories are often constructed which are formally or logically absolutely free of error, yet psychologically full of errors that no logic whatever could correct. We have, therefore, to consider at least the most important conditions which determine the manner of our inferences.

The right which lawyers possess of studying these questions, so far as they lie in our field, is of modern establishment. According to Hillebrand[126] the theory of knowledge has to-day broken up into individual theories, involving the certain needs of special fields of knowledge. The place of the epistomologists, who are professionals and beyond the pale of individual disciplines, is now taken by the representatives of those disciplines and each works expressly on his own epistomological problem. Our especial problem is the drawing of inferences from the material presented to us or brought together by our efforts, just as in other disciplines. If we set ourselves the task of determining the procedure when subjecting the fundamental principles of our work to revision and examining their utility, we merely ask whether the process is voluntary or according to fixed laws; and having cleared up that point we ask what influence psychological conditions exercise on the situation. It is, indeed, said that thinking is a congenital endowment, not to be learned from rules. But the problem is not teaching the inferrer to think; the problem is the examination of how inferences have been made by another and what value his inferences may have for our own conclusions. And our own time, which has been bold enough to lay this final conclusion in even the most important criminal cases, in the hands of laymen, this time is doubly bound at least to prepare all possible control for this work, to measure what is finally taken as evidence with the finest instruments possible, and to present to the jury only what has been proved and repeatedly examined.

It might almost seem as if the task the jury trial sets the judge has not been clearly perceived. A judge who thinks he has performed it when he has cast before the jury the largest possible mass of testimony, more or less reviewed, and who sees how people, who perhaps for the first time in their lives, are involved in a court of law, who perhaps see a criminal for the first time, and are under these circumstances the arbiters of a man’s fate,--a judge who sees all this and is satisfied, is not effective in his work. Nowadays more than ever, it is for the judge to test all evidence psychologically, to review what is only apparently clear, to fill out lacunae, and to surmount difficulties, before he permits the material brought together in a very few hours to pass into the jury’s hands. According to Hillebrand, much that seems “self-evident” shows itself dependent on definite experience attained in the process of hundreds of repetitions in the daily life; the very impression of self-evidence is frequently produced by a mere chance instinct about what should be held for true. Hume has already shown how the most complex and abstract concepts are derived from sensation. Their relation must be studied, and only when we can account for every psychic process with which we have to concern ourselves, is our duty properly fulfilled.