281 
there are two ways in which we may draw a picture in our 
minds (however imperfect that picture may be) of the mode of 
exercise of that Will, namely (1), by a series of independent 
fiats ; or (2) by adapting means to an end, and working 
according to established laws. Now, the ordinary course of 
Nature shows that such is at any rate an ordinary mode of 
operation of that Will ; as, for example, where we see an 
apparatus adapted to the laws of reflection and refraction of 
lffiht in such a manner as to produce images on the retina. 
What, then, should we expect a 'priori to find in our examina- 
tion of Nature ? Surely, as we must picture to our minds a 
skill of contrivance far beyond our own, we might expect that 
the greatest human intellect would be able to follow but a 
small portion of the contrivances actually existing; conse- 
quently, that at the boundary of what we have been able to 
make out there should be dim indications of something of the 
same kind stretching out into the unknown ; but yet, at the 
same time, that there should be no indication that such a chain 
of causation would of itself alone suffice for the explanation of 
the system of Nature. 
And this, it seems to me, is precisely what we find. To 
revert to our illustration of the eye : we have seen that as 
regards the formation of images on the retina it acts as an 
ordinary optical instrument in a way which we can fully follow; 
but when the images are formed, what then? We find the 
retina to contain an exquisitely delicate network of nerves 
collected into the optic nerve, and thence running into the 
brain. These nerve-fibres seem as evidently adapted to fulfil 
an end as the telegraph wires which run along a road or railway, 
though how they act in conveying an impression into the 
brain is as yet unknown; and how the impression so con- 
veyed into the brain is capable of affecting our minds is 
shrouded in the deepest mystery. Again, the form and 
character of the cornea, crystalline lens, &c., are such as 
admirably fit them for their office of refracting the rays of 
light ; but how came they to have this form and character ? 
We perceive that there are vessels evidently subservient to 
their growth and nutrition, and that is pretty nearly all we 
can explain about it. 
There is thus, as it seems to me, no inconsistency in accept- 
ing the theory of evolution as a guide in our researches, and 
yet rejecting it as sufficient of itself alone to explain the whole 
order of nature. The rejection of it as a guide, and the 
acceptance of it as an axiom of universal application, seem to 
me to be founded alike, though in different ways, upon an 
exaggerated estimate of the extent of human knowledge. To 
r 2 
