306 THE PRINCIPLES OF SCIENCE. 



In all matters of judicial evidence, we must bear in 

 mind the necessary occurrence from time to time of un- 

 accountable coincidences. The Roman jurists refused for 

 this reason to invalidate a testamentary deed, the wit- 

 nesses of which had sealed it with the same seal. For 

 witnesses independently using their own seals might be 

 found to possess identical ones by accident 11 . It is well 

 known that circumstantial evidence of apparently over- 

 whelming completeness will sometimes lead to a mistaken 

 judgment, and as absolute certainty is never really attain- 

 able, every court must act upon probabilities of a very 

 high amount, and in a certain small proportion of cases 

 they must almost of necessity condemn the innocent 

 victims of a remarkable conjuncture of circumstances . 

 Popular judgments usually turn upon probabilities of 

 far less amount, as when the palace of Nicomedia, and 

 even the bedchamber of Diocletian, having been on fire 

 twice within fifteen days, the people entirely refused to 

 believe that it could be the result of accident. The 

 Romans believed that there was a fatality connected with 

 the name of Sextus. 



'Semper sub Sextis perdita Roma fuit. 1 



The utmost precautions will not provide against all 

 contingencies. To avoid errors in important calculations, 

 it is usual to have them repeated by different computers, 

 but a case is on record in which three computers made 

 exactly the same calculations of the place of a star, and 

 yet all did it wrong in precisely the same manner, for no 

 apparent reason P. 



n Possunt autem omnes testes et uno annulo signare testamentum. 

 Quid enim si septem annuli una sculptura fuerint, secundum quod Pom- 

 ponid visum estl 'Justinian,' ii. tit. x. 5. 



See Wills on ' Circumstantial Evidence,' p. 148. 



P ' Memoirs of the Royal Astronomical Society,' vol. iv. p. 290, quoted 

 by Lardner, 'Edinburgh Review,' July 1834, p. 278. 



