It was none the less a perfectly ordinary horse, such as convergent evolution has produced in many of the places that life is to be found. They have always understood a great deal more than they let on. It is difficult to be sat on all day, every day, by some other creature, without forming an opinion about them.

Adams treats a familiar animal—the horse—as if it were an alien species, using mock-scientific language (“convergent evolution”) to defamiliarize the ordinary and make it funny. The joke turns into a sly ethical observation: animals that live in close, unequal relationships with humans inevitably learn to read us, judge us, and form “opinions” about our behavior. The line also satirizes human self-importance; we assume we are the only observers with inner lives, while Adams suggests the ridden creature may be the sharper critic. Humor here functions as a prompt toward empathy and a reminder that intelligence and perspective are not uniquely human.