To restore a text from the documental evidence available we must know and weigh the causes which tend to vitiate this evidence in its various kinds.
Legitimate doubt arises when the evidence pro et contra of documental and intrinsic probability is equal, or nearly equal, or when documental probability points strongly to one side and intrinsic probability to another.
When it is conscientiously obtained, it is arrived at by handi capping, more or less heavily, intrinsic probability as compared with documental probability, or by raising the minimum of probability which shall qualify a reading for admission into the text until it is in agreement with the notions of the editor.
There is, however, one class of cases in which no conclusion may be drawn, documental and intrinsic probability both failing us.
