Page:Mind (New Series) Volume 8.djvu/87

 TESTIMONY AND AUTHORITY. 73 expert in the arts of observation and experiment. We must be satisfied in such cases not merely that there has been no confusion between true observation and inference but of much more besides. In scientific experiment we depend not only on the observer's power of seeing, but on his skill in doing. We must be satisfied not only that nothing present was missed, but also that the contriving and opera- tive skill of the observer were such as to ensure that every- thing that could possibly be present was present. Natural endowment of sense counts for much keenness of eyesight, touch, hearing. But practice and experience are factors equally important, especially in those inquiries depending on manipulative skill or on the use of complex instruments or methods. Facts of this character must be understood in the following pages by the terms skill or capacity. The conditions, as we have seen, then, on which the credibility of a single witness depends, supposing his mean- ing first to have been correctly apprehended, comprise (1) his freedom from bias, (2) his sincerity and care, (3) his accuracy of memory and expression, (4) his opportunities or means for knowing, (5) his capacity or skill relative to the matter in question. The relationship of the criteria to each other may be exhibited diagrammatically thus : f2. Sincerity and care of the wit- A. Those relating to the"! | ness (conscientiousness), conveyance of infor- mation. 1 3. Accuracy of memory and ex- l pression. 1. Freedom from bias or un- conscious influences. 4. Opportunities or means for knowing. 5. Capacity or skill relative to the matter in question. It may be admitted that testimony is of the highest authority if it is deliberately given by a sincere person having had opportunities for cognizance of the matter and adequate powers of observation or judgment, who is care- ful and capable of accurate memory and expression, and is free from the influence of bias. But in place of the apparently simple question, " Is or is not this testimony xeliable?" there now seems to be a multitude of questions, Those relating to the acquisition of infor- mation.