26 PIONEERS OF EVOLUTION. 



belief in immortality as due to ghosts and appari- 

 tions which appear in dreams. " When sleep has 

 prostrated the body, for no other reason does the 

 mind's intelligence wake, except because the very 

 same images provoke our minds which provoke them 

 when we are awake, and to such a degree that we 

 seem without a doubt to perceive him whom life has 

 left, and death and earth gotten hold of. This Na- 

 ture constrains to come to pass because all the senses 

 of the body are then hampered and at rest through- 

 out the limbs, and cannot refute the unreal by real 

 things." 



In the fifth book Lucretius deals with origins 

 of the sun, the moon, the earth (which he held to be 

 flat, denying the existence of the antipodes); of life 

 and its development; and of civilization. In all this 

 he excludes design, explaining everything as pro- 

 duced and maintained by natural agents, "the masses, 

 suddenly brought together, became the rudiments of 

 earth, sea, and heaven, and the race of living things." 

 He believed in the successive appearance of plants 

 and animals, but in their arising separately and di- 

 rectly out of the earth, " under the influence of rain 

 and the heat of the sun," thus repeating the old 

 speculations of the emergence of life from slime, 

 " wherefore the earth with good title has gotten and 

 keeps the name of mother." He did not adopt Em- 

 pedocles's theory of the " four roots of all things," 

 and he will have none of the monsters the hippo- 

 griffs, chimeras, and centaurs which form a part of 



