The Theory of Sexual Selection. 405 
how, out of such a feeling as a cause, the beauty of 
organic nature may have followed as an effect. 
Now we have already seen how the theory of sexual 
selection supposes this to have happened. But 
against this theory a formidable objection arises, and 
one which I have thought it best to reserve for treat- 
ment in this place, because it serves to show the 
principal difference between Mr. Darwin’s two great 
generalizations, considered as generalizations in the 
way of mechanical theory. For while the theory of 
natural selection extends equally throughout the whole 
range of organic nature, the theory of sexual selection 
has but a comparatively restricted scope, which, more- 
over, is but vaguely defined. For it is obvious that 
the theory can only apply to living organisms which 
are sufficiently intelligent to admit of our reasonably 
accrediting them with esthetic taste—namely, in 
effect, the higher animals. And just as this con- 
sideration greatly restricts the possible scope of the 
theory, as compared with that of natural selection, so 
does it render undefined the zoological limits within 
which it can be reasonably employed. Lastly, this 
necessarily undefined, and yet most important limita- 
tion exposes the theory to the objection just alluded 
to, and which I shall now mention. 
The theory, as we have just seen, is necessarily 
restricted in its application to the higher animals. 
Yet the facts which it is designed to explain are not 
thus restricted. For beauty is by no means restricted 
to the higher animals. The whole of the vegetable 
world, and the whole of the animal world at least as 
high up in the scale as the insects, must be taken as 
incapable of zsthetic feeling. Therefore, the extreme 
