An adherent of sexual selection can, however, easily object that these theories, however sound and sensible they may be, still leave the main point in Darwin’s thesis quite unaffected. When trying to prove the existence of an æsthetic judgment in birds, he did not lay so much stress upon decorative plumage itself as upon the fact of its being displayed in the presence of the hen. If secondary sexual characters had their only purpose in facilitating recognition between individuals of the same species, then these elaborate performances would be quite superfluous. And this argument can of course be further strengthened by reference to the musical and dancing entertainments given by the males. Any theory which leaves these activities unexplained must therefore be regarded as incomplete. In Mr. Wallace’s _Darwinism_ due attention has indeed been paid to pre-nuptial performances. But his explanation, viz. that the dancing and singing, etc., are only the effect of an inner impulse to movement and activity which accompanies sexual maturity,[270] can but incompletely unriddle the problem. For the purpose of affording an outflow to a surplus of vigour or of discharging a nervous tension, activities of a far simpler character would have been sufficient. As, however, amongst birds with gorgeous plumage every movement in the display tends towards exhibiting their splendour with the greatest possible _éclat_, an influence upon the hen cannot be argued away. It is, as Darwin remarks, impossible to believe that the Argus pheasant, for instance, should have developed precisely such a curious and peculiar sort of dance, through which his beautiful dress is so effectively shown forth, if this dance had been of no effect upon its spectators.[271] This effect cannot, as has been shown above, be considered an æsthetic one. It is also difficult to believe that the hen, as it has been suggested, should appreciate the secondary sexual characters as signs of greater or smaller vital force, and thus prefer not the most beautiful, but the most vigorous and ardent mate.[272] Whether it is founded on an æsthetic judgment or on an estimation of the force displayed, her conscious choosing seems to be alike improbable.