1X8 THE HISTORY OF BIOLOGY 



temperament was as pacific as his interests were universal, he endeavoured 

 everywhere to reconcile and to unite. At one time he speculated upon a 

 universal science in which all human knowledge was to be represented by 

 short symbols; on other occasions he worked for the union of the different 

 Christian Churches. The same efforts to reconcile opposed views likewise 

 govern his natural philosophy. Thus, he seeks to show that the Church's 

 doctrine of the omnipotence of God, and natural science's mechanical ex- 

 planation of the universe are by no means mutually exclusive, but are capable 

 of being harmonized. 



Leibniz.' s raonad theory 

 As a natural philosopher Leibniz took the atomic theory as his starting-point. 

 As he found it impossible, however, to derive consciousness and the mani- 

 festations of the soul in general from the movements of atoms, he sought a 

 way out of the difficulty by assuming a universe composed of units of an ideal, 

 not of a material, character. The idea for this theory he found through using 

 the microscope, which had then just been invented; by this means it is 

 possible to see that every drop of water swarms with life and that life exists 

 everywhere, even where the eye cannot see it; it was thus but a short step 

 to the conclusion that the smallest particles of matter are life-principles — 

 not dead atoms, but living "monads," as Leibniz called them. These monads 

 he conceives as being of infinite variety, some of a higher type, others of a 

 lower. The human soul is one such monad, which has consciousness; the life 

 of animals consists of lower monads, unconscious, but percipient; the monads 

 of plants live, but are not percipient; the monads of inanimate nature are in 

 an indifferent state, as in a dreamless sleep, the human body being composed 

 of these latter monads. The activity of the monads is not motion, as the atomic 

 theory supposed, for motion is something relative, but their ultimate quality 

 can only be conceived as force — conatus, as Leibniz calls it. By this means 

 they each, in a higher or lower degree, obtain some notion of existence. On 

 the other hand, they do not react upon one another, their interrelation being 

 governed by a harmonious cosmic order, originally created by God, who is 

 the supreme monad. Thus, the human body functions by force of the harmony 

 of existence parallel and in tune with the soul, like two clocks which go 

 exactly alike. The kingdoms of nature and of grace act similarly towards one 

 another. — All this extremely abstract speculation might at first sight appear 

 foreign to all that is meant by natural science. Leibniz has, however, actually 

 exercised great influence on natural research, partly by awakening interest 

 in life, both in the great multiplicity of its manifestations and in its most 

 minute forms, and, above all, by insisting upon the idea of force as the basis 

 of natural phenomena instead of movement, which even Descartes believed. 

 And his endeavour to reconcile the kingdoms of nature and of grace, which 

 may appear foreign to the ideas of natural research of our own day, would 



