 But this could mean that Mark is the common source of the other two ("priority"), or that it derives from both ("posteriority"), or even that it is an intermediary in transmission from one to the other—in other words, many such arguments can support both Marcan priority and its rivals.Famously, the so-called "Lachmann fallacy", concerning the order of pericopae in Mark, was once used to argue for Marcan priority but is now seen as a largely neutral observation.Modern arguments for or against Marcan priority tend to center on redactional plausibility, asking, for example, whether it is more reasonable that Matthew and Luke could have written as they did with Mark in hand, or that Mark could have written as he did with Matthew and Luke in hand, and whether any coherent rationale can be discerned underlying the redactional activity of the later evangelists.