NATURAL SELECTION AND NATURAL THEOLOGY 259 



the properties which cats have in common with other living things, 

 and while it may leave the hardship which cats bring to mice as 

 much of a puzzle as ever, natural selection is a strictly scientific 

 explanation of the point in question: the specific adjustment of 

 cats to the life of mice ; for, when all the conditions of the prob- 

 lem are known, it shows that we have, through the discoveries of 

 Darwin and Wallace, the same rational confidence that the life of 

 mice will modify the. structure of cats as we have for judicious 

 expectation that a current in the ocean will modify the course of 

 a ship ; although there is no reason to suppose, in either case, that 

 our confidence is more than reasonable and judicious; for we find 

 in nature no ultimate or final reason why the current should modify 

 the ship's course, or why the environment of cats should modify 

 their structure, except that the fact is so. Neither do we find in 

 nature any explanation of cats which seems to us perfectly satis- 

 factory to mice. 



It is obvious, however, that in so far as natural selection 

 accounts for all that is distinctive or specific in the structure of 

 living things, it accounts, at the same time and to exactly the 

 same degree, for all that their structure does; and that the web 

 the spider makes out of silk is no harder to understand than the 

 web the radiolarian makes out of protoplasm. 



So far as Paley's reasoning concerns the zoologist, it is a trea- 

 tise on the minor premise of his argument ; for no one in his day 

 seems to have thought that the major premise needs defence or 

 is open to attack, although the modern zoologist must ask whether 

 we are sure that nothing but mind accounts for watches. In 

 science we hold a thing accounted for when, certain conditions 

 being given, we have every reason to expect it; and Paley's 

 major premise that nothing but mind accounts for watches is 

 worthless, if the conditions which, being given, are good reasons 

 for expecting watches are physical. 



If a watchmaker were to tell us he was so distracted by care 

 or grief that he did not know what he was about when he made 

 the watch, no one would think this incredible ; for we are familiar 

 with the unconscious performance of equally delicate and com- 

 plicated and definite series of bodily movements, as in piano 

 playing; nor would we see any reason to doubt the assertion of 



