HARVARD LAW REVIEW. VOL. IV. MAY 15,1890. NO. 2. THE BURDEN OF PROOF. IF we conceive to ourselves a legal system in which the pleadings, if any there be, admit of only one defence, that of mere ne- gation, — that is to say, where not merely the pleading is negative in form, but where no other than a purely negative defence is open under it, and all other defences, as if they were cross actions, require a separate trial ; we can see that the phrase Burden of Proof {Onus probandiy Beweislasty Fardeau de la preuve) may have a very simple meaning. Under such a system the defendant has nothing to prove ; it is the plaintiff, the actovy who has the duty of proving, while the defendant, the reuSy has only the negative function of baffling the plaintiff. If, on the other hand, we picture a system in which any defence whatever may be open upon a plea of general denial, in which a defendant who stands upon the record as merely denying, may, at the trial, turn himself into a plaintiff by setting up an affirmative defence, and the original plaintiff may become a defendant by merely denying this new case of his adversary ; then we observe that so simple a conception of the proof and the duty of proving, is no longer possible. Either party may have it, and it may shift back and forth during the trial, because each party in turn may set up, in the course of the trial, an affirmative ground of fact, which, if he would win, he must, of course, make good by proof. We can no longer say when the pleading is over and
