The praetor's formula

The praetor is a magistrate elected for one year, with no required technical training in law. His task is not to say who is right, but to organize the trial: accept or refuse the action requested, negotiate the exact wording of the formula with the parties, then send them before a judge. The moment the two parties accept that wording is called the litis contestatio: it "consumes" the disputed right into the formula, which can no longer be changed before the iudex.

The iudex is a private citizen, chosen by the parties or drawn from a list, with no standing power: he judges this one case, then becomes a private individual again. He hears the evidence and the pleadings, then applies the text received from the praetor. The judgment is nothing more than the output of that program: condemn or acquit, nothing else.

When civil law provides no action for a situation that nonetheless deserves protection, the praetor invents one: an actio utilis, modeled on an existing action and extended by analogy, or an actio ficticia, which orders the judge to assume as true a fact that is not yet true. The Publician action is the most famous example (Gaius, Institutes, 4, 36): it protects the buyer in good faith who has not yet completed the year of possession required for usucapio, by ordering the judge to reason as if that period had already elapsed.

The exceptio is a negative condition inserted into the order to condemn. The judge condemns only if the intentio proves true and the exceptio proves false; in every other case, he acquits. A perfectly established debt thus gives way to a fraud by the creditor or an agreement not to claim it: the formula lets one say yes to the claim and no to its enforcement, in the same breath.

Before the formula, the legis actiones reigned, verbal rites of absolute rigidity: a single wrong syllable lost the case. Gaius (Institutes, 4, 30) tells of a litigant who lost his suit for speaking of "vines" when the statute he invoked spoke of "trees" cut down in general: the judge, bound by the letter of the rite, could do nothing for him. The lex Aebutia, in the second century BC, legitimized the formulary procedure as a more flexible alternative; Augustus's leges Iuliae judiciorum, in 17 BC, made it the ordinary path of civil trial throughout the Empire.

Medieval England had its own system of formulas: writs, royal briefs each opening a precise form of action, with its own conditions and its own procedure. These forms of action were abolished in the nineteenth century, but the historian F. W. Maitland could still write, in 1909, that they "still rule us from their graves".