Cormac McCarthy's great Western novel All the Pretty Horses uses horses to symbolize manhood. Typically in the old West, guns were the definition of a man. But here, it's a man's horse:
Finally he said that among men there was no such communion as among horses and the notion that men can be understood at all was probably an illusion.
Whereas Jimmy Blevins kills another man to get his gun back, John Grady risks his life to go back into Mexico to recover his horse. Remember when Lacey and John keep asking if Jimmy stole his horse? They don't believe it's his, just as they don't believe he's a real man. In the end, they're right: he is kid attempting to be a man.
Early in a man's life, his horse is young and wild.
As he was drifting to sleep his thoughts were of horses and of the open country and of horses. Horses still wild on the mesa who'd never seen a man afoot and who knew nothing of him or his life yet in whose souls he would come to reside forever.
But as a man comes into his own so does his horse. It's not a horse, it's HIS horse. He trained it. He branded it. He pilots it. It is his identity and manhood:
But there were two things they agreed upon wholly and that were never spoken and that was that God had put horses on earth to work cattle and that other than cattle there was no wealth proper to a man.
Because the horses are often the object of desire, the reason behind almost every conflict, and the vehicle by which the men move around the country, they play an integral role in every aspect of the story. A man is often measured according to how he handles a horse, what he knows about horses, and how many horses he has. In this way they symbolize the quest for manhood, for reputation and for power. John Grady begins his new life aboard a horse and demonstrates his manhood not only through fighting but in his ability to work with horses, and to judge which horses are valuable.
Though he does not get much of what he wants, he does return to Texas on horseback as more of a man, and the horse symbolizes this success as well.