78 HARVARD LAW REVIEW. clearly relevant, and not merely slightly so ; it must not barely afford a basis for conjecture, but for real belief; it must not merely be remotely relevant, but proximately so. Again, it must not unnec- essarily complicate the case, or too much tend to confuse, mislead, or tire the minds of that untrained tribunal, the jury, or to with- draw their attention too much from the real issues of the case. Now in the application of such standards as these, the chief appeal is made to sound judgment ; to what our lawyers have called, for six or seven centuries at least, the discretion of the judge. Deci- sions on such subjects are not readily open to revision ; and, when revised, they have to be judged of in a large way ; this is expressed by saying that the question is whether the discretion has been abused, has been unreasonably exercised. Doubtless, in some classes of such cases, there may have grown up a sub-rule which limits the discretion. In such cases, since there is not an unfettered discretion, an ordinary additional question of law arises as to the application of this subsidiary rule. But, in general, the question of law is not an ordinary one, because it ties itself to an outside, non- legal standard ; viz., that of good sense, common experience, the sound judgment of men of affairs. When, for example, on a ques- tion of negligence in driving a horse across a railroad, you offer evidence of a single instance where a third party drove safely over at another time, under like conditions; or, in another case, evi- dence of ten separate instances of doing this; and in both cases it is rejected ; it is easy to see that a revising court might properly enough sustain both rejections, while themselves disapproving of both ; — sustaining and yet disapproving of the first, because the evidence was slight and conjectural, and yet might be thought by a trial judge sufficiently relevant and helpful ; and the second, because, while it seemed, in point of quality, fairly clear and strong and probative, it tended to confuse the case by its multiplication of instances, and because there were other simpler ways of proof open to the party, such as the opinion of experienced observers or a view by the judge or jury. In such cases it is a question of where lies the balance of practical advantage. To discuss such questions, as is sometimes done, on the bare ground of relevancy, — even if we introduce the poor notion of legal relevancy, as contrasted with logical relevancy, — tends to obscure the nature of the inquiry. There is, in truth, generally, no rule of law to apply in answering such questions as whether the evidence, although probative, is too slight, conjectural,
