60 NATURE AND LIFE. 
special way. Geometry and mechanics, in their specula- 
tion, separate material points from forces, while biology 
teaches us to keep them bound together in an indestructible 
and necessary unity. The science of motions and of the 
forms they take, shows us only the outside of the energy of 
the universe. The science of life, on the contrary, unveils 
to us its throbbing heart and its splendid plan. Such is 
the measureless and priceless service it yields to knowledge 
and to discussion. Descartes, and those who attempt in 
our day to revive his system by deducing physics from 
mechanics, and physiology from physics, by explaining the 
higher through the lower, as Auguste Comte says, by for- 
bidding any endeavor to conceive first principles by the aid 
of last principles—all those philosophers, whatever their 
merit in other respects, have misunderstood the lessons 
yielded by the living being in its twofold physiological and 
psychological relation. The evidences of soul making one 
and the same with life might have displayed to their view 
images of the soul and of life throughout the universe, 
instead of blind and misleading geometrism. They would 
have understood that ciphers and diagrams do not solve 
every thing, that computation is not the only method. 
That which does solve every thing is the soul, because it 
alone embraces every thing, or at least discovers in itself 
alone, rapt in abstraction, instinctive secret affinities with 
all. Besides, the certain and enduring fame of Descartes 
is great enough to permit us, without fear of dimming its 
deserved lustre, to pronounce sentence of impotence upon 
any attempts made in our day toward the introduction into 
natural philosophy of false principles borrowed from his 
teachings. The guidance and inspiration which modern 
biological science owes to them attest the increasing honor 
paid to the ideas of Leibnitz.* 
1 This article, written during the siege of Paris at the ambulance of 
Conflans, where I was serving as physician, having access only to a few 

