ILLUSTRATIONS OF THE LOGIC OF SCIENCE. 213 



which it is inferred. That space is not immediately perceived is now 

 universally admitted; and a mediate cognition is what is called an 

 inference, and is subject to the criticism of logic. But what are we to 

 say to the fact of every chicken as soon as it is hatched solving a prob- 

 lem whose data are of a complexity sufficient to try the greatest 

 mathematical powers ? It would be insane to deny that the tendency to 

 light upon the conception of space is inborn in the mind of the chicken 

 and of every animal. The same thing is equally true of time. That time 

 is not directly perceived is evident, since no lapse of time is present, and 

 we only perceive what is present. That, not having the idea of time, 

 we should ever be able to perceive the flow in our sensations without 

 some particular aptitude for it, will probably also be admitted. The 

 idea of force at least, in its rudiments is another conception so early 

 arrived at, and found in animals so low in the scale of intelligence, that 

 it must be supposed innate. But the innateness of an idea admits of 

 degree, for it consists in the tendency of that idea to present itself 

 to the mind. Some ideas, like that of space, do so present themselves 

 irresistibly at the very dawn of .intelligence, and take possession of the 

 mind on small provocation, while of other conceptions we are prepos- 

 sessed, indeed, but not so strongly, down a scale which is greatly ex- 

 tended. The tendency to personify every thing, and to attribute human 

 characters to it, may be said to be innate ; but it is a tendency which is 

 very soon overcome by civilized man in regard to the greater part of 

 the objects about him. Take such a conception as that of gravitation 

 varying inversely as the square of the distance. It is a very simple law. 

 But to say that it is simple is merely to say that it is one which the 

 mind is particularly adapted to apprehend with facility. Suppose the 

 idea of. a quantity multiplied into another had been no more easy to the 

 mind than that of a quantity raised to the power indicated by itself 

 should we ever have discovered the law of the solar system ? 



It seems incontestable, therefore, that the mind of man is strongly 

 adapted to the comprehension of the world ; at least, so far as this goes, 

 that certain conceptions, highly important for such a comprehension, 

 naturally arise in his mind ; and, without such a tendency, the mind 

 could never have had any development at all. 



How are we to explain this adaptation ? The great utility and in- 

 dispensableness of the conceptions of time, space, and force, even to the 

 lowest intelligence, are such as to suggest that they are the results of 

 natural selection. Without something like geometrical, kinetical, and 

 mechanical conceptions, no animal could seize his food or do anything 

 which might be necessary for the preservation of the species. He 

 might, it is true, be provided with an instinct which would generally 

 have the same effect ; that is to say, he might have conceptions differ- 

 ent from those of time, space, and force, but which coincided with them 

 in regard to the ordinary cases of the animal's experience. But, as that 

 animal would have an immense advantage in the struggle for life whose 



