PARTS OF ANIMALS, I. i. 



common, and afterwards the specific peculiarities ; 

 or begin straightΛvay A\'ith the particular species.* 

 Hitherto this has not been definitely settled. And 

 there is a further point Λvhich has not yet been 

 decided : should the student of Nature follow the 

 same sort of procedure as the mathematician follows 

 in his asti'onomical expositions — that is to say, 

 should he consider first of all the phenomena which 

 occur in animals, and the parts of each of them, and 

 having done that go on to state the reasons and the 

 causes ; or should he follow some other procedure ? 

 Furthermore, we see that there are more causes '' 

 than one concerned in the formation " of natural 

 things : there is the Cause ybr the sake of ivhich the 

 thing is formed,*^ and the Cause to vvhich the begin- 

 ning of the motion is due.^ Therefore another point 

 for us to decide is which of these two Causes stands 

 first and which comes second. Clearly the first is 

 that which Ave call the " Final " Cause — that for the 

 sake of which the thing is formed — since that is 

 the logos ^ of the thing — its rational ground, and 

 the logos is always the beginning for products of 

 Nature as well as for those of Art. The physician 

 or the builder sets before himself something quite 

 definite — the one, health, apprehensible by the 

 mind, the other, a house, apprehensible by the 

 senses ; and once he has got this, each of them 

 can tell you the causes and the rational grounds 

 for everything he does, and why it must be done 

 as he does it. Yet the Final Cause (purpose) and the 

 Good (Beautiful) ^ is more fully present in the works 

 of Nature than in the vvorks of Art. And moreover 

 the factor of Necessity is not present in all the 

 works of Nature in a similar sense. Almost all 



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