138 GALILEO AND HIS JUDGES. 



I need not add that I consider the future discovery 

 of such explanation as so improbable, that one may 

 practically dismiss the idea, but I should be sorry to 

 deny it as being conceivably possible. 



The other, and opposite, error is that of certain 

 well-meaning but ill-informed persons, who imagine 

 that the Copernican theory is even now doubtful and 

 liable to be overthrown liable, I mean, in a real 

 and practical sense, and not by distant contingencies, 

 such as those at which I have just hinted, and which 

 may be considered as shadowy and intangible. I do 

 not suppose that amongst educated men there are 

 many such scientific recusants ; but at any rate it 

 may be useful to give a short summary of the evi- 

 dence on which the Copernican conclusion is based. 

 In doing this I fear I shall tire the patience of my 

 readers by partly repeating Galileo's own arguments, 

 which I have already quoted in discussing the Dia- 

 logue. This cannot easily be avoided, for much of 

 his reasoning is so sound and so forcible, that after 

 the lapse of more than two centuries we can add 

 but little to it. On the other hand, there are grave 

 mistakes that must be shunned ; and, moreover, there 

 have been discoveries made since the day when the 

 Dialogue was written, of inestimable importance. 



The best way of treating the question is to resume 

 the history of astronomical research from the point 

 where we dropped it ; that is, at the time when 

 Galileo first made known to the world the result of 

 his observations. 



