XII. Demonstration that all Matter is heavy. By the Rev. William 

 Whewell, B.D. Fellow of Trinity College and Professor of Moral 

 Philosophy. 



[Read February 22, 184].] 



The discussion of the nature of the grounds and proofs of the most 

 general propositions which the physical sciences include, belongs rather 

 to Metaphysics than to that course of experimental and mathematical 

 investigation by which the sciences are formed. But such discussions seem 

 by no means unfitted to occupy the attention of the cultivators of physical 

 science. The ideal, as well as the experimental side of our knowledge 

 must be carefully studied and scrutinized, in order that its true import may 

 be seen ; and this province of human speculation has been perhaps of late 

 unjustly depreciated and neglected by men of science. Yet it can be 

 prosecuted in the most advantageous manner by them only : for no one can 

 speculate securely and rightly respecting the nature and proofs of the truths 

 of science without a steady possession of some large and solid portions of 

 such truths. A man must be a mathematician, a mechanical philosopher, 

 a natural historian, in order that he may philosophize well concerning 

 mathematics, and mechanics, and natural history ; and the mere metaphy- 

 sician who without such preparation and fitness sets himself to determine 

 the grounds of mathematical or mechanical truths, or the principles of 

 classification, will be liable to be led into error at every step. He must 

 speculate by means of general terms, which he will not be able to use as 

 instruments of discovering and conveying philosophical truth, because he 

 cannot, in his own mind, habitually and familiarly, embody their import in 

 special examples. 



Acting upon such views, I have already laid before the Philosophical 

 Society of Cambridge essays on such subjects as I here refer to ; especially a 



