right he claims, he will not be heard, because if he merely says I claim such1 a thing  as my right, it does not suffice unless he at once shows his right, as where he says of  which such an ancestor etc.2 And if he does show his right, and3 supports his intentio,  that does not suffice unless he at once produces proof,4 as will be explained below,  because he who proves nothing falls from his intentio,5 nor does it matter whether he  proves nothing at all or proves it inadequately, as will be explained below [in the  portion] on the litis contestatio.6
An exception is also given by reason of the narratio, by saying now one thing, now another.
 An exception also arises for the tenant by reason7 of the narratio, as where [the demandant]  changes his intentio,8 now saying one thing now another, contrary to or  different from the first, except where that is permitted, or in his narratio departs  from his writ, so that the narratio does not agree with the writ or does not say what  amounts to it. And so if, when he has once put forward his intentio and the writ afterwards  falls because of error, when he later begins to sue by another writ he changes  his intentio, that first put forward, completely or in part, [A fortiori if he fraudulently  withdraws from one writ so that he may change his intentio in another, though it may  be urged that new subject matter requires a new causa,] [because] though the writ is  changed, the action ought not to be changed,9 nor the intentio first put forward varied  because of the several writs,10 since they are put forward under the same action.
An exception also lies for the tenant because of res judicata.
 The exception of res judicata lies for the tenant, as where the ancestor of the demandant  or one of his heirs has lost the thing claimed by judgment in a proprietary action,  as by the grand assise or the duel, or by the jury on which he placed himself; this  exception is peremptory because it completely destroys the action.11 And so if it was  by a concord and fine made, which is equally peremptory. It is called a final concord  because it puts an end to suits, as where the tenant says that there was once a plea in