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The principles of this school of historical criticism have a 
negative and a positive aspect. The negative portion of the 
system consists in an examination of the authorities on which 
the received views of historical truth rest, and the rejection 
of those views which are based on no historical founda- 
tion. For example, it was found that the belief in a large 
portion of the received Roman history rested on the testimony 
of authors who lived several hundred years after the events 
which they professed to record ; and although some of their 
authorities might be called ancient, they were quite modern 
compared with the events themselves. It was also discovered 
that the fathers of Roman history had but few written sources 
of information, and that such as existed were of a very meagre 
character, and that their reports were founded on traditions, 
poems, and annals of very questionable authority. As it 
would occupy too much space for me to enter on this portion 
of the subject, I must refer to what I apprehend is the best 
manual of historical criticism existing in the language, the 
works of Sir Gr. C. Lewis. I can only express my regret that 
he did not live to give us a complete organon of historical 
criticism, and to reduce its detached rules and canons to a 
scientific system. 
This negative side of historical criticism, although it is 
capable of being pushed too far in incautious hands, is one of 
considerable validity. It has now been carried into every 
region of historical inquiry ; and to it we are indebted that 
large numbers of incredibilities have now taken their proper 
place in the regions of the fabulous. Though I have called 
this the negative side of historical criticism, it has a positive 
aspect. It has disinterred a large number of important facts, 
and placed them on a solid basis of evidence as historical truths. 
But Niebuhr also thought that he could establish a positive 
method of a very different character. It seemed very hard to 
the inquirer to be obliged to abandon to the regions of un- 
certainty so large a portion of the history of man. Niebuhr 
thought that he could reconstruct history out of the mass of 
ruins under which it had been buried, through the crumbling 
of materials in past ages. It would be impossible for me to 
give here a full account of the principles on which this 
attempted reconstruction was based. It will be sufficient to 
say that one of the chief instruments relied on was to supply 
the gaps of history by plausible conjecture, which, if I recollect 
rightly, Niebuhr called the power of historical divination. It 
will be evident that the number of theories by which these 
gaps may be covered over, though not actually indefinite, are 
very numerous. One person could theorize as well as another, 
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