Only one reading can be original. Though this might seem unnecessary to say there are still exegetes who think that text criticism is unimportant. Yet when we recall that the author of a text could only write one original, then we have to try to find that original using the tools we have at hand. Only the reading which best satisfies the external and internal criteria can be original. That is, only the oldest and best attested reading can be original.
External criteria are the most important.
That is, the oldest manuscripts are more important than the youngest. Internal criteria are less important than external. The Greek tradition is more important than the versions. Manuscripts should be weighed, not counted. Certain text families are superior to others.