ANCIENT SCIENCE. 27 



of Athens," Plato is represented raising his hand towards heaven as 

 the region of his Ideas, while Aristotle indicates his field of research 

 by pointing to the earth. But, however great may have been the 

 difference between the two philosophers, Aristotle appears to have 

 adopted a system as inherently subjective as that of his predecessor. 

 Thus, for example, he teaches that in order to know the nature of a 

 thing we must first consider the end for which it is made. The results 

 of his speculations and researches present a strange intermixture of 

 truthful observations and unfounded opinions. How much some of 

 the speculations of Aristotle on physical subjects consist of merely 

 verbal distinctions and deductions from preconceived dogmas, may be 

 seen from the following short resume of some of his reasonings on 

 astronomical subjects : 



He begins by stating that as planes are measurable in two direc- 

 tions, and lines in only one, so bodies have magnitudes in three direc- 

 tions. Body is therefore made complete by three magnitudes, and 

 three is specially the number of perfection, being used in the observ- 

 ances by which honour is paid to the gods. We speak also, says- 

 Aristotle, of three things as we do of all. (The allusion here seems to 

 be to the separate grammatical forms used for the dual number by 

 the Greeks, as their plural number does not, as with us, indicate two- 

 or more, but three or more persons or things. This last argument is 

 an example of the assumption that the facts of nature must correspond 

 with merely verbal distinctions.) As matter is then made complete 

 by three, the same must be the case with motion ; and, in fact, there 

 can be but three simple motions motion towards the centre, motion 

 from the centre, and motion round the centre. The first two are 

 rectilineal motions, and these two are motions natural to the four 

 elements, since it is the nature of earth and water to move downwards 

 towards the centre, and of fire and air to move upwards from the 

 centre. The heavenly body which revolves in a circle cannot there : 

 fore be fire, as some have supposed ; nor can it be any other of our 

 four elements, since to these only the rectilineal motions to or from 

 the centre are natural. By violence, indeed, a body may be moved 

 contrary to its natural motion, as when a stone is thrown upwards : 

 but such motions being contrary to nature speedily cease. It would, 

 therefore, be unreasonable to suppose that the continuous and eternal 

 circular motion of the heavenly body can be contrary to nature. 

 And it would be inconsistent with Goodness that any being should be 

 employed in constraining by violence the heavenly body to circular 

 motion contrary to its own nature. The perpetual task of thus pro- 

 viding violent and ceaseless rotation would condemn the moving soul 

 to pain and an unhappy fate. It must, therefore, be the nature of the 

 heavenly body to revolve in a circle, and it was a mistake on the part 

 of the ancients (it seems curious to find Aristotle speaking of the 

 ancients) to think that the heavens must be supported by the feigned 



