a terrifying black horse which the driver of the soul can never hope entirely to understand or subdue

Aristotle is never a very considerate writer. Indeed, he regularly asks a great deal of his readers, namely that they keep the whole of his immensely complex analysis of reality vividly before them at all times. But there is a much more important reason for this almost universal misunderstanding, and that is the gross improbability of Aristotle's idea itself--the very suggestion itself that the whole world could be shown to be really flawlessly rational if we but looked closely enough. We look around us and we see that nature, like ourselves, does indeed seem to strive for patterns; and we realize that if it were not for these patterns we should be unable to make any sense of our perceptions of separate experiences and make predictions which will be valid for the future; but we also see, as Plato taught us to do, that these patterns are never actually realized. We have to perceive with our minds, not our eyes, where things are tending, for our eyes give us only an infinite sequence of unique perceptions--similarities but no identities among our experiences in this perpetual flux. Surely, we say, this points clearly to some kind of an irreducible brutishness and irrationality in the very stuff of the world: how, we ask, could Aristotle possibly have avoided that conclusion?

--Thomas Gould, "Aristotle and the Irrational," Arion, Vol 2, No 2, Summer 1963 (pg 64)