loo PRESENT-DAY RATIONALISM 



Now this is precisely what Evolution represents. 



There may yet be added another feature. If a watch 

 gets out of order it has to be taken to a watchmaker to 

 be repaired ; but organisms have self-reparative powers, 

 so that a wound will heal up without external assistance. 



However clever a human watchmaker may be, Nature 

 is incomparably the better of the two ; even though not 

 a single structure in the world may be regarded as ideally 

 perfect. 



Darwin gives us his ideas of how he conceived a human 

 eye was evolved from a pigment spot by means of Natural 

 Selection, first observing : " I have felt the difficulty too 

 keenly to be surprised at others hesitating to extend the 

 principle of Natural Selection to so startling a length ". 



" If we must compare the eye to an optical instrument, 

 we ought in imagination to take a thick layer of trans- 

 parent tissue [itself as well as the following having arisen 

 through Natural Selection] with spaces filled -w'lih fluid, 

 and with a no^e sensitive to light, beneath, and then 

 suppose every part of this layer to be conti^inally changing 

 slowly into density, so as to separate into layers of dif- 

 ferent densities and thicknesses, placed at different distances 

 from each other, and with surfaces of each layer changing 

 inform. [We may ask where are all these things to be 

 got, and why do they arise in Nature ?] Further we must 

 suppose that there is a power, represented by Natural 

 Selection or the survival of the fittest, always intently 

 watching each slight alteration in the transparent layers ; 

 and carefully preserving each which, under varied cir- 

 cumstances in any way or in any degree, tends to produce a 

 distincter ijnage. We must suppose each new state of the 

 instrument to be multiplied by the million [this is impos- 

 sible unless this sequence has occurred in a multitude of 

 individuals instead of one only] ; each to be preserved 



