PLURALITY OF WORLDS. 27 



relations. All are alike in general configuration, all 

 subject to the same laws of gravitation, revolution, 

 and rotation on axis. 1 Solar light and heat are com- 

 mon to all, with diversities only of degree. Eeflected 

 light is conveyed to several of them, in some propor- 

 tion to their distance from the sun, and by the agency 

 of moons. 



It is hardly conceivable that such physical relations 

 and resemblances as these should exist without the 

 presence of life, and intelligence also, in the worlds so 

 related to us. Can the earth be thus peopled with all its 

 various living forms, and the other planets be mere brute 

 globes of matter, with no breath of vitality upon them ? 

 The argument, as one of strong presumption, might 

 almost be vested in this simple question. If a single 

 case were taken for special illustration, it might be 

 that of Venus and the earth. The magnitude of the 

 two planets is almost exactly the same. The earth is 

 c seen from Venus, as Venus is by us ; the only differ- 

 ence depending on Venus being one-third nearer to 

 the sun. The mass and density of both globes are 

 nearly alike. The time of rotation on axis differs by 

 forty minutes only. The larger reception of light and 

 heat by Venus, and the appendage of a moon to the 

 earth (facts not perhaps without relation to each other), 

 are the sole physical differences obvious to us between 

 the two planets. Can one of them be devoid of all 

 life, while on the other it is swarming so variously and 



1 In his ( Calcul des Probabilites/ Laplace shows that there are 

 4,000,000 to one in favour of the forty-three motions of rotation and 

 revolution of planets and satellites from east to west being produced 

 by one and the same original cause. 



