PHILOSOPHY OF NATURE—LEIBNITZ’S IDEAS. 5Y 
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. . . . Every 
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, ef seg. 
