45. General estimates of comparative excellence are at once shown to be insufficient by the fact that excellence itself is of various kinds: a document may be ‘good’ in one respect and ‘bad’ in another. The distinction between soundness and correctness, for instance, lies on the surface. One MS will transmit a substantially pure text disfigured by the blunders of a careless scribe, another will reproduce a deeply adulterated text with smooth faultlessness. It therefore becomes necessary in the case of important MSS to observe and discriminate the classes of clerical errors by which their proper texts are severally disguised; for an authority representing a sound tradition can be used with increased confidence when its own obvious slips have been classed under definite heads, so that those of its readings which cannot be referred to any of these heads must be reasonably supposed to have belonged to the text of its exemplar. The complexity of excellence is further increased by the unequal distribution of the mental or semi-mental causes of corruption; while they too can be observed, classified, and taken into account, though with less precision than defects of mechanical accuracy. Where the documentary witnesses are not exclusively MSS having continuous texts in the original language, but also, for instance, translations into other languages or quotations by later authors, similar deductions are required in order to avoid being misled as to the substantive text of their exemplars. Thus allowance has to be made for the changes of phraseology, real or apparent, which translators generally are prone to introduce, and again for those which may be due to the defects or other peculiarities of a given language, or the purpose of a given translation. In quotations account must in like manner be taken of the modifications, in-
