The Chariot Allegory of Plato is a very important part of the Western -- and World -- spiritual and philosophical tradition. It presents a rich metaphor for the soul and its journey.
The soul is portrayed as a charioteer (Reason), and two winged steeds: one white ('spiritedness', the irascible, boldness
and one black (concupiscence, the appetitive, desire). The goal is to ascend to divine heights -- but the black horse poses problems. The chariot figure itself is just the beginning, however; it leads to a revealing portrayal of the 'ups and downs' of the spiritual or philosophical life.