Natural theology. 79 



formation of an image by the refraction of rays of 

 light, at least as manifestly as the glasses and tubes 

 of a dioptric telescope are suited to that purpose, 

 it concerns not the proof which these afford of de- 

 sign, and of a designer, that there may perhaps 

 be other parts, certain muscles, for instance, or 

 nerves in the same eye, of the agency or effect of 

 which we can give no account, any more than we 

 should be inclined to doubt, or ought to doubt, about 

 the construction of a telescope, viz. for what purpose 

 it was constructed, or whether it were constructed 

 at all, because there belonged to it certain screws 

 and pins, the use or action of which we did not 

 comprehend. I take it to be a general way of in- 

 fusing doubts and scruples into the mind, to recur 

 to its own ignorance, its own imbecility : to tell us 

 that upon these subjects we know little ; that little 

 imperfectly ; or rather, that we know nothing pro- 

 perly about the matter. These suggestions so fall 

 in with our consciousness as sometimes to pro- 

 duce a general distrust of our faculties and our con- 

 clusions. But this is an unfounded jealousy. The un- 

 certainty of one thing does not necessarily affect 

 the certainty of another thing. Our ignorance of 

 many points need not suspend our assurance of a few. 

 Before we yield, in any particular instance, to the 

 skepticism which this sort of insinuation would in- 

 duce, we ought accurately to ascertain whether our 

 ignorance or doubt concern those precise points 

 upon which our conclusion rests. Other points are 

 nothing. Our ignorance of other points may be of 



