312 SMALL VALUE OF TESTIMONY 



Upon difficult subjects it is astonishing to what an 

 extent the multiplication of these little differences 

 will in the end mislead us, if we do not keep the 

 whole chain carefully in view ; for in twenty suc- 

 cessive occurrences we may attend carefully to each, 

 and compare it with the one immediately before it, 

 and find the very same apparent similarity in each 

 of those comparisons; and yet the differences, 

 unseen in the individual cases, may so mount up in 

 the aggregate as that the last may be unlike the 

 first or even the very reverse of it. With careless 

 observers, who are satisfied with a few of the ex- 

 ternal and more obvious circumstances, that is much 

 more frequently the case ; and as they who publish 

 their opinions or conclusions to the world are not 

 always the most close and accurate observers, that 

 is the reason why so many errors have crept into 

 the science and the systems of natural history ; and 

 as many of these errors are fortified by high au- 

 thority, and all of them by some authority (for there 

 always are people so forward in their belief that the 

 very fact of being in print is an authority to them), 

 they are very difficult to be reduced. 



The only means of doing that is by going back 

 to the beginning of the series, that is, to nature 

 itself; and hence the superiority of knowledge 

 which we get from our own actual observation to 

 knowledge of any other kind. But it is only a little 

 way that that will carry us without assistance. We 

 must see the whole succession ; and the cases in 

 which we have that opportunity are few, while those 

 for which a whole lifetime is too short are very 

 many. It is in those cases of which we can per- 

 sonally observe only a part that the co-operation 

 of society is of much value. We have the record 

 of the past for that part of the succession which 

 happened before we were born, and we have the 

 intelligence of the present time for that which takes 

 place when we are not present ; and thus, though 



