46 kARVARD LAW REVIEW, before the trial begins, " the proof belongs here and cannot belong elsewhere ; the onus probandi is on the plaintiff and it cannot shift." If now we further conceive that under this last system the action of the tribunal passing upon questions of fact is sub- ject to review, so that an appellate court may have to consider whether such a body as a jury has acted reasonably in weighing evidence and counter-evidence, and whether the judge who has presided over a trial by jury has rightly ordered the trial, and rightly instructed the jury as to comparing and weighing evi- dence, we may see that questions will be introduced into legal discussion as to the respective duties of the parties in producing evidence at different points of the trial, and in meeting evidence produced against them, which may be wholly absent from another system where there is no such judicial revision of the method of using and estimating the evidence. The conception is brought to light of producing evidence to meet the pressure of an adversary's case, a duty which may belong to either party, and to both parties in turn ; and this conception now takes its place in legal dis- cussion and requires its own terminology." Let us further suppose that this new topic, — new in the sense of requiring now to be discriminated and discussed, — the mere duty of producing evidence, belonging thus to neither party exclu- sively, and to each by turns, gets also called the burden of proof ; it becomes plain that, as regards the meaning of this term, we have advanced from a region of simple and clear ideas to one which is likely to be full of confusion. We have, in fact, proceeded from conceptions which we may roughly describe as those of the Roman law and of some later systems founded upon it, to those which fill and perplex the books of our common law to-day. If now, furthermore, recognizing that there are these two wholly distinct notions of the burden of proof, both called by the same name, we then observe that, as regards one of them, the duty of establishing, it is often a very difficult thing to determine whether a given defence be an affirmative one or not, and so to decide which party has the burden of the proof in this sense, and that the common-law judges have fallen into the way of giving as the test,^ as the regular professional " rule of thumb," for tell- ^ "The proper test is, which party would be successful if no evidence at all were given." Alderson, B., in Amos v. Hughes, i Moo. & Rob. 464.
