300 DEVELOPMENT AND PURPOSE CHAP. 



transition to that which exists later, as, in fact, becoming it, 

 of its own nature and without the aid of any adventitious 

 concomitants. This unconditional continuous becoming 

 is the ideal to which mechanical explanation tends, and this 

 once again is in direct opposition to the teleological con- 

 ception, in accordance with which all the elements and 

 constituent processes of an arrangement are indefinitely 

 modifiable, and are in fact so modified as best to ensure 

 the working out of a purpose which is subsequent to their 

 action. Under the teleological category, in fact, it looks 

 at least on the surface as though the future goes to deter- 

 mine the present. 



Whether this first impression of teleological determina- 

 tion can hold in the end, we shall consider further at a 

 later stage. We have first to point out that in our surface 

 view both mechanism and teleology are together necessary 

 for the full explanation of our lever. For merely to 

 analyse the law of the lever's action is not to show how the 

 lever comes to be where it is, while if we extend the 

 c mechanical ' explanation so as to include the whole story 

 of its formation and insertion into the machine, we shall 

 have to take account of the engineer's mind and of the 

 purpose which the machine is to serve. That is to say, 

 the 'full 5 mechanical explanation will involve the teleo- 

 logical. But conversely, the teleological involves the 

 mechanical. The precise function to be fulfilled by the 

 lever is indeed prescribed by the purpose of the machine 

 and the general arrangement, but the way in which this 

 particular lever performs that function is to be understood 

 only by studying its peculiar reactions. Mechanical actions 

 are the units out of which the working process is con- 

 structed, just as the physical bolts and cogs are the units 

 of which the arrangement, as a material structure, is built 

 up. The full explanation of our piece of mechanism then 

 must include both the analysis of its own operation and a 

 statement of the teleological system in which it forms a part. 



3 . We have seen that our mechanical explanation is forced 

 ultimately to take account of the constructive purpose of 

 the engineer, in order to explain how the lever came to be 



