318 Literary Notices. 



by which, it is established. In the absence of any sufficient original 

 investigation into the grounds upon which any proposition that re- 

 ceives the sanction of authoi'ity rests, the authority, if supposed 

 trustworthy, affords a convenient resting place, and establishes in 

 the mind of every one who thinks it more likely to be right than 

 wrong, a certain balance of evidence in favour of the proposition it 

 affirms. The evidence is, however, of this character — Smith is an 

 intelligent man — he has studied the subject, — he says so, and he is 

 likely to be right. True, but he is also likely in a greater or less 

 degree to be wrong. A high degree of probability is all that we 

 can expect to attain to ; but after the probableness of a statement 

 reaches a certain point, it becomes reasonable to act upon it, and to 

 regard it as true, but faith in the most probable statement should 

 never hinder the perception of the improbability, however small it 

 may be, that remains attached to it, and which cannot be regarded 

 as a constant and ascertained quantity, but must be esteemed as a 

 quantity which further discovery may at any time change the value 

 of, either in the direction of its augmentation or its diminution. 



The "Wrangler" who puts forth the pamphlet on'the " Theories of 

 Copernicus and Ptolemy," deserves the thanks of those who recog- 

 nize the truth of the propositions we have thus sketched out. It 

 is no doubt common to assume that the Copernican theory rests 

 upon a more thoroughly complete mass of evidence than can be 

 claimed for it ; but its defenders are only bound to show that, as com- 

 pared with the Ptolemaic theory it is sustained not only by a balance 

 of probability, but by enough probability to be a legitimate basis for 

 thought and action. That the conception of gravitation as an uni- 

 versal force, resident in, or essential to, all matter, and causing all 

 particles to attract each other proportionably to their mass, and in an 

 inverse proportion to their distance, could not be maintained by any- 

 thing like proof. Astronomers have to recognise repulsive forces as 

 well as attractive ones, and we know of no argument in favour of the 

 supposition that the attraction of gravitation is not correlative with 

 any other mode of force, but always existing without change as an 

 absolute property of each particle of matter, and in eternal antago- 

 nism to all repellant forces. Views of this kind have been several 

 times put forward in our pages. 



The "Wrangler" contends, not for the truth of Ptolemaic 

 astronomy, but that its major requirements are not improbable, and 

 it is here that most philosophers will disagree with him, and we 

 are not sure that he sufficiently recognises tho evidence of im- 

 probability that attaches to the best proved systems, or sufficiently 

 admits that some amount of improbability is no ground for 

 disbelief. It is important, however, to bear in mind the doubts and 

 objections of the " Wrangler," which are well put, though not, it 

 strikes us, at all new. Our solar system may be but a portion of a 

 greater system, and the centre of gravity of the whole may be 

 nearer or further than astronomers fancy. This will be generally 

 admitted, so will the analogy between the particles of a small body, 

 and that of sun and the planets regarded as particles of the giant 

 whole, The constitution of nebula?, the appearance of a repulsive 



