§ 76. proper counter-claim on the part of the defendant, as an inequitable proceeding which he would refuse to allow, though the civil law placed no obstacle in the way. But the effect of such an exceptio doli, granted on the ground of a counter-claim properly set up, was not a set-off, but the acquittal of the defendant (provided he succeeded in proving his counter-claim in judicio), and that quite regardless of the extent of such counter-claim. Thus, what the praetor had done in the case of actiones stricti juris was not to introduce the principle of set-off, but to compel the plaintiff, by indirect means (viz. on pain of forfeiting his whole claim), to deduct the amount of the counter-claim himself at the time of commencing his action, or rather before the granting of the formula, i.e. before the litis contestatio. The next step in the development of compensatio was effected by a rescript of Marcus Aurelius, which provided that where an exceptio doli was inserted in the formula in a judicium stricti juris on the ground of an admissible counter-claim, such exceptio should operate by way of set-off. In all cases, therefore, where an exceptio doli was thus inserted, the defendant, on making good his plea, was not for that reason entitled to a simple acquittal in respect of his whole debt, but only to an acquittal to the extent of his counter-claim. The necessity, however, for the praetorian remedy by exceptio doli remained unaffected, and if the defendant in an actio stricti juris failed to get such an exceptio inserted, he was debarred from advancing a set-off. In other words, the defendant in a judicium stricti juris was still obliged to set up his counter-claim in jure with a view to having an exceptio doli embodied in the formula. The civil law still refused to acknowledge any right of compensatio, and, where the principle was admitted, it operated, as before, not ipso jure, but only ope exceptionis, i. e. by the praetorian law. But an exceptio, like this exceptio doli of the rescript, the purpose of which was to give effect to a counter-claim, was a very anomalous kind of exceptio. It is, as we have seen (sup. pp. 197, 204), the essence of an exceptio that it operates to acquit the defendant 'by way of exception.' And yet the purpose of this particular exceptio doli was in effect to determine, not whether the defendant should be con demned to pay, but what he should be condemned to pay 7. Such § 76. an exceptio was not in reality an exceptio at all, because it did not imply an exception from, but rather an interpretation of, the order to condemn. The right of the plaintiff to have judgment given in his favour did not simply depend on the defendant proving, or not proving, his exceptio doli, and the condemnatio continued, notwithstanding the exceptio, to be conditional on the truth of the intentio. The only question now was the amount in which the defendant would be condemned. In the same way it had formerly been the practice of the praetor, in granting a bonorum emtor (sup. p. 211) a right of action, to qualify such right by adding the words 'cum deductione.' That is to say, if the bonorum emtor sued for a debt due to the bankrupt, the judge was instructed to condemn the defendant 'cum deductione,' i. e. to condemn him in the balance due from him to the bankrupt after deducting the amount, if any, due from the bankrupt to him. The condemnatio thus became an incerti condemnatio, even where the object of the bonorum emtor's claim was a certum 8. The result was that an exceptio doli, when inserted for the purpose of enforcing a counter-claim, became the means whereby actiones stricti juris were in all cases converted into actions with a condemnatio incerti. Assuming then that an exceptio doli has been inserted in the formula and that the defendant has succeeded in establishing his counter-claim in the action, a question will arise as to the true effect to be given by the judge to such counter-claim. It might be urged, on the one hand, that the plaintiff's claim should not be regarded as 7 Paulus, in defining an exceptio in 1. 22 pr. D. de except. (44, 1): 'exceptio est condicio, quae modo eximit reum damnatione, modo minuit damnationem,' takes account of this exceptio doli which operates to produce a set-off, but his own words 'condicio quae minuit damnationem' serve, at the same time, to bring out very clearly the contradiction involved in such a definition. The case of an argentarius (banker) was treated somewhat differently. The praetor required a banker to sue his customer on a current account 'cum compensatione,' because the relationship between banker and customer, which is based on a series of payments and counter- § 76. cancelled pro tanto till the moment when the judge has actually acknowledged the justice of the defendant's plea of set-off. On the other hand, it might be said that the plaintiff's claim ought to be treated as cancelled pro tanto from the moment when the claim and the counter-claim first co-existed. The question would be of importance where, for example, the plaintiff's claim carried interest with it and the defendant's counter-claim did not. If the former view were taken, the plaintiff might claim interest in the meanwhile; if the second view were taken, he had no such right. The question was this: where the defendant raises a plea of set-off, ought such a plea to be taken as signifying a disposition, a willingness, on his part, to conclude an agreement of set-off with the plaintiff (because, if so, the set-off could only operate prospectively and not retrospectively), or ought it simply to be taken as an allegation of fact (viz. an allegation of the existence of a counter-claim) which, without any act on the part of the defendant, and without any intention on the part of the plaintiff, operates automatically, as it were, to limit the binding force of the plaintiff's right to the difference in the amount of the two claims? In the latter case compensatio must be regarded as dating back retrospectively to the moment in which the counter-claim first came into existence. Roman jurisprudence decided in favour of the second alternative and expressed the view it adopted in the rule: ipso jure compensari. In all cases, however, the effect of the coming into. existence of a counter-claim as such is not an immediate cancelling of the original claim, but merely a provisional linking together of claim and counter-claim. In order to convert a mere joinder into an extinction one of two things must happen: either the parties must voluntarily agree to set-off their reciprocal demands, or the defendant must successfully establish his plea of set-off in the action. In either case the original claim becomes irrevocably bound up with the counter-claim, and is thereby rateably cancelled. Up to the moment however, when the two claims have become irrevocably bound up, payment of one of the debts, or even set-off of a different counterclaim, will operate to sever the provisional joinder of the claims. A counter-claim thus constitutes, in all cases, a mere ground of set-off operating ipso jure, the immediate effect of which is-and it is an effect which may be reversed again by other processes-to weaken § 76. the force of the creditor's claim in favour of the debtor. But a counter-claim never constitutes a ground of extinction operating ipso jure. Where an extinction results from a counter-claim, such a result does not arise ipso jure, but is invariably based on an agreement or a judicial decision, and in the case of a judicium stricti juris this judicial decision still depends, as it did before, on the prior grant of an exceptio doli by the praetor. Accordingly, the power of a counter-claim to extinguish a claim which is sued for, is still due, as it always was, to the praetorian, and not to the civil law; the counter-claim still operates ope exceptionis and not ipso jure, in spite of the rule as to ipso jure compensari. Justinian subsequently made a plea of set-off a ground of defence operating ipso jure in the processual sense of the term. According to Justinian's law a plea of set-off may be advanced at any stage of the action, and the judge need not be expressly authorized to take such a plea into account. The only condition required is that the counter-claim shall be easy of proof (liquida), i. e. the evidence necessary to establish it must not delay the final decision of the case. With this restriction Justinian admitted pleas of set-off in all cases whatever, whether the claims arose ex dispari causa or ex eadem causa, and even where the claim was asserted by means of a real action, for example, a real action for damages. Certain specified cases only were excepted, e.g. the actio depositi directa. But even in Justinian's law the effect of a counterclaim, from the point of view of private law, is not to cancel the other claim ipso jure, but merely to suspend it-a further act (viz. an agreement or a judgment) being necessary to convert the suspension into an extinction. L. I D. de compensat. (16, 2) (MODESTINUS): Compensatio est debiti et crediti inter se contributio. L. 21 eod. (PAULUS): Posteaquam placuit inter omnes id, quod invicem debetur, ipso jure compensari, si procurator absentis conveniatur, non debebit de rato cavere, quia nihil compensat, sed ab initio minus ab eo petitur. L. 11 eod. (ULPIAN.): Cum alter alteri pecuniam sine usuris, alter usurariam debet, constitutum est a divo Severo, concur Аа § 76. rentis apud utrumque quantitatis usuras non esse prae standas. § 30 I. de act. (4, 6): In bonae fidei autem judiciis libera potestas 3. As to the extinction of obligations by litis contestatio, v. sup. According to the civil law capitis deminutio (even capitis demi- L. 2 § 1 D. de cap. min. (4, 5): Ait Preetor: QUI QUAEVE, The words of the text (Gajus iv. in the case of bonae fidei judicia (where |