Let us suppose a notorious burglar found in possession of a jemmy; it is admitted on all hands that he will use it as soon as he gets a chance; there is no doubt about this; how perverted should we not consider the ingenuity of one who tried to persuade us we were wrong in thinking that the burglar compassed the possession of the jemmy by means involving ideas, however vague in the first instance, of applying it to its subsequent function.

If any one could be found so blind to obvious inferences as to accept natural selection, “or the preservation of favoured machines,” as the main means of mechanical modification, we might suppose him to argue much as follows:- “I can quite understand,” he would exclaim, “how any one who reflects upon the originally simple form of the earliest jemmies, and observes the developments they have since attained in the hands of our most accomplished housebreakers, might at first be tempted to believe that the present form of the instrument has been arrived at by long-continued improvement in the hands of an almost infinite succession of thieves; but may not this inference be somewhat too hastily drawn?  Have we any right to assume that burglars work by means analogous to those employed by other people?  If any thief happened to pick up any crowbar which happened to be ever such a little better suited to his purpose than the one he had been in the habit of using hitherto, he would at once seize and carefully preserve it.  If it got worn out or broken he would begin searching for a crowbar as like as possible to the one that he had lost; and when, with advancing skill, and in default of being able to find the exact thing he wanted, he took at length to making a jemmy for himself, he would imitate the latest and most perfect adaptation, which would thus be most likely to be preserved in the struggle of competitive forms.  Let this process go on for countless generations, among countless burglars of all nations, and may we not suppose that a jemmy would be in time arrived at, as superior to any that could have been designed as the effect of the Niagara Falls is superior to the puny efforts of the landscape gardener?”

For the moment I will pass over the obvious retort that there is no sufficient parallelism between bodily organs and mechanical inventions to make a denial of design in the one involve in equity a denial of it in the other also, and that therefore the preceding paragraph has no force.  A man is not bound to deny design in machines wherein it can be clearly seen because he denies it in living organs where at best it is a matter of inference.  This retort is plausible, but in the course of the two next following chapters but one it will be shown to be without force; for the moment, however, beyond thus calling attention to it, I must pass it by.