RESULTS AND LIMITS OF SCIENTIFIC METHOD. 431 



appears to represent the probability that our inference 

 will be mistaken. I demur to the assumption that there 

 is any necessary truth even in such fundamental laws of 

 nature as the Indestructibility of Matter, the Conservation 

 of Force, or the Laws of Motion. Certain it is that men 

 of science have recognised the conceivability of other laws, 

 or even investigated their mathematical conditions. Sir 

 George Airy investigated the mathematical conditions of 

 a perpetual motion (vol. i. p. 256), and Laplace and New- 

 ton discussed various imaginary laws of forces incon- 

 sistent with those so far observed to operate in the 

 universe (vol. ii. pp. 304, 392). 



The laws of nature, as I venture to regard them, are 

 simply general propositions concerning the correlation of 

 properties which have been observed to hold true of 

 bodies hitherto observed. On the assumption that our 

 experience is of adequate extent, and that no arbitrary 

 interference takes place, we are then able to assign the 

 probability, always less than certainty, that the next 

 object of the same apparent nature will conform to the 

 same law. 



Iiifiniteness of the Universe. 



We may safely accept as a satisfactory scientific hypo- 

 thesis the doctrine so grandly put forth by Laplace, who 

 asserted that a perfect knowledge of the universe, as it 

 existed at any given moment, would give a perfect know- 

 ledge of what was to happen thenceforth and for ever 

 after. Scientific inference is impossible, unless we may 

 regard the present as the necessary outcome of what is 

 past, and the necessary cause of what is to come. To 

 the view of Perfect Intelligence nothing is uncertain. The 

 astronomer can calculate the positions of the heavenly 

 bodies when thousands of generations of men shall have 



