I divided each soul into three—two horses and a charioteer; and one of the horses was good and the other bad: …. The right-hand horse is upright and cleanly made … his colour is white, and his eyes dark; he is a lover of honour and modesty and temperance, and the follower of true glory; he needs no touch of the whip, but is guided by word and admonition only. The other is a crooked lumbering animal … he has a short thick neck; … of a dark colour, with grey and blood-shot eyes …. he mate of insolence and pride, shag-eared and deaf, hardly yielding to whip and spur. Now when the charioteer beholds the vision of love …. and has his whole soul warmed through sense       – Plato, Phaedrus

 

Charioteer = the reason,

The black horse is the symbol of the sensual or concupiscent element of human nature.

The white horse also represents rational impulse, but the description, ‘a lover of honor and modesty and temperance, and a follower of true glory