SCIENCE AND DEMONSTRATION 257 



to whom it is ascribed, or belongs to the epoch and country to 

 which it is assigned ; (2) that it has not been interpolated or cor 

 rupted by the interference of other hands. The proper ascription 

 of a document is ascertained partly by external, and partly by 

 internal evidence. Evidence of authorship, or of time or place 

 of composition, is said to be external when derived from sources 

 other than the document itself. The chief external evidence in 

 most cases will be found in what tradition, oral or written, has 

 handed down in each case. If tradition, whether oral or 

 written, ascribes the composition of a work to a certain author, 

 time, or place, and if there is no special reason to doubt the reliability 

 of its source, we can be morally certain that the tradition is cor 

 rect : for the simple reason that men are naturally truthful 

 &quot; nemo gratis mendax&quot; and that human testimony under due 

 conditions is a sufficient criterion of truth. If, for instance, we 

 find all contemporary and immediately subsequent writers, who 

 refer to a work, ascribe it to a certain author, this may in itself 

 suffice to settle the question. But, on the other hand, it may 

 perhaps merely create an initial presumption in favour of the 

 alleged authorship, and form a basis for further critical inquiry. 

 This is true especially of all works that come down to us from 

 the centuries prior to the invention of printing which dates from 

 the end of the fifteenth century. The origins of all traditions as to 

 authorship, previous to this latter date, call for careful scrutiny ; 

 for in those earlier ages it was comparatively easy to give cur 

 rency to writings by falsely representing them as the works of 

 eminent authorities ; and this facility was largely availed of. 



Where external evidence is doubtful or conflicting, or where 

 there is no such evidence at all, the internal evidence, derived 

 from the work itself, may prove to be very valuable. Internal 

 evidence must, of course, be very conclusive before it can upset a 

 strong, uniform, and apparently well-grounded tradition as to 

 authorship ; but as a matter of fact it has exploded many such 

 traditions ; and it is constantly furnishing conclusive settlements 

 to disputed questions regarding the provenance of documents. 

 Internal evidence is of various kinds : (a) a comparison of the 

 style of the work in question with that of other works known for 

 certain to come from the supposed author, will be of more or 

 less assistance in determining authorship ; () references, in the 

 document, to events the dates of which are known, will help to 

 fix the date of composition (the possibility and the fact of prophecy, 

 VOL. II. 17 



