PHILOSOPHY OF NATURE -LEIBNITZ'S IDEAS. 57 



ous as it is irresistible, to fill up the voids that he observes 

 in the series, and to imagine rationally possible species in 

 order to do it. In this way he sees beforehand the exist- 

 ence of some being unknown in reality, just as he foresees, 

 in accordance with the laws of celestial mechanism, the ex- 

 istence of a planet never yet observed. This doctrine, 

 which Leibnitz had deduced from the principle of continu- 

 ity, and from that of the " sufficient reason," has been un- 

 deniably rich in results for the sciences. We name a late 

 instance, taken from chemistry. " The synthesis of neutral 

 fats," says Berthelot, " not only enables us to make artificial- 

 ly the fifteen or twenty natural fatty substances heretofore 

 known, but allows us also to foresee the formation of some 

 hundreds of millions of similar fatty bodies. . . . Ever}' 

 substance, every phenomenon, represents, we may say, one 

 link involved in a more extended chain of similar and cor- 

 related substances and phenomena. . . . Without quitting 

 the range of reasonable expectation, we may assume to 

 conceive the general types of all possible substances, and to 

 produce them." * 



Another general idea is precisely that of type. We 

 cannot define type better than by using the old expression, 

 " creature of reason." In truth, it is a grouping together 

 of elements which maintain themselves in an harmonious 

 arrangement in such wise as to form a whole, conceived by 

 the reason as perfect. Such ideal and rational creation, 

 answering to certain conditions of fixity, necessity, and 

 generality, becomes a pattern, a standard to which the 

 mind refers and compares existing beings outside of itself. 

 The mind thus has the power of using reality to abstract 

 from it certain conditions which it groups in a higher, 

 clearer, in brief, in a truer, order than that manifested in 

 the outward world. We may add that the creation of 

 types is an imperative need for the mind ; it shows it in 



1 " Organic Chemistry," vol. ii., p. 800, ct seq. 



