In this section, the author reveals the substantive nature of the prejudice objection. It is noted, that the praetor ex officio always takes care of the appropriate sequence between two processes. Two processes cannot co-exist together. It is only about the existence of two parallel claims, about the competition of the two rights to sue (actiones in the material sense). One right has had to give way in favor of another. Under exceptio praejudicii both suits are always based on the same cause, but the «common item» only is not enough to justify an objection. In addition to the cause, should be a common aim and success of both actions, that is, there should be a real competition. For example, in the hereditary cases actions competition would exist if the bequeathed things is vindicated by means of other action than hereditatis petitio (vindication, recovery of a debt, etc.). 

Keywords: history of civil procedure; praejudicium; praejudice; issue preclusion.