Agreements, for example, between Old Latin and Old Syriac witnesses may sometimes be due to common influence from Tatian's Diatessaron. The genealogical relationship of the text and families of witnesses. Mere numbers of witnesses supporting a given variant reading do not necessarily prove the superiority of the reading. For example, if in a given sentence reading x is supported by twenty manuscripts and reading y by only one manuscript, the relative numerical support favoring x counts for nothing if all twenty manuscripts should be discovered to be the copies made from a single manuscript, no longer extant, whose scribe first introduced that particular variant reading. The comparison, in that case, ought to be made between the one manuscript containing reading y and the single ancestor of the twenty manuscripts containing reading x .
Witnesses are to be weighed rather than counted.
At the same time, however, since the relative weight of the several kinds of evidence differs for different kinds of variants, there should be no merely mechanical evaluation of the evidence. In general, the more difficult reading is to be preferred, particularly when the sense appears on the surface to be erroneous but on more mature consideration proves itself to be correct. Alter a less refined grammatical form or a less elegant lexical expression in accord with contemporary. Intrinsic Probabilities depend upon considerations of what the author was more likely to have written. It is obvious that not all of these criteria are applicable in every case.