GENERATION OF ANIMALS, II. vi. 



" this is how they are always formed," and regard 

 this as a starting-point (first principle) in these cases, 

 make a mistake, nor do they even succeed in stating 

 tlie necessity involved in the cause. Their argument 

 is this : What is limitless has no starting-point ; but the 

 cause is a starting-point, and what is always is limit- 

 less ; therefore (says Democritus) to ask for a cause 

 in connexion with an}i:hing of this kind {sc, anything 

 that ahrays is) is the same as trying to discover a 

 starting-point in something that is limitless. Yet on 

 this line of argument, on the strength of which they 

 undertake to dispense with trying to discover the 

 cause, there will be no demonstration of any single 

 one of the " eternal " things. It is obvious, however, 

 that demonstrations of many of these (some of them 

 things which ahvays come to be, some things which 

 always are) do in fact exist. For instance, the angles 

 of a triangle are always equal to two right angles, 

 and the diagonal of a square is always incommensur- 

 able with the side ; in both of these cases we have 

 something " eternal," yet there is a cause for them 

 and they are demonstrable. Thus it is right to say 

 that we cannot undertake to try to discover a starting- 

 point (a first principle) in all things and evervthing ; 

 but it is not right to deny the possibihty in the case 

 of all the things that always are and that always come 

 to be ; it is impossible only vvith the first principles 

 of the eternal things, for of course the first principle 

 does not admit of demonstration, but is apprehended 

 by another mode of cognition." Now with those 

 things that are " immutable," the first principle is 



hy we perceive that the tiltimate figure in mathematics is a 

 triangle. Again (114.3 b 1) in demonstrations, voO? appre- 

 hends the immutable {aKivrfra) and primary definitions. 



217 



