I have already argued that the instinct of political affection is stimulated by the vivid realisation of its object.

Since therefore it is easier, at least for uneducated men, to realise the existence of beings like than of beings unlike themselves, affection for one's like would appear to have a natural basis, but one likely to be modified as our powers of realisation are stimulated by education.
Again, since most men live, especially in childhood, among persons belonging to the same race as themselves, any markedly unusual face or dress may excite the instinct of fear of that which is unknown.

A child's fear, however, of a strangely shaped or coloured face is more easily obliterated by familiarity than it would be if it were the result of a specific instinct of race-hatred.

White or Chinese children show, one is told, no permanent aversion for Chinese or white or Hindoo or negro nurses and attendants.

Sex love, again, even when opposed by social tradition, springs up freely between very different human types; and widely separated races have been thereby amalgamated.