His horse thinks old is an example of?

"His horse thinks old is an example of" is an incomplete sentence. To understand what it's an example of, we need more context. Here are some possibilities:

* Personification: The sentence could be an example of personification, giving human-like qualities to an animal. Horses can't think in the way humans do, so the sentence is attributing human-like thought to the horse.

* Figurative Language: It could be a metaphor or simile used to describe a situation. For example, "His horse thinks old is an example of a slow and steady pace." This metaphor suggests that the horse, despite its age, still possesses the ability to move with grace and agility.

* A Beginning of a Story: It could be the start of a story or a riddle, leading to a more complex explanation.

Please provide more context or complete the sentence so I can give you a more specific answer.