Realists believe that there is an exactly understandable way the world is—one that describes processes independent of our intervention. Anti-realists, however, believe realism is too ambitious—too hard. They believe we pragmatically describe our interactions with nature—not truths that are independent of us.
In nature, according to nonlocality, properties of one particle may depend on what we choose to measure or manipulate with a second particle, even at great distances. In quantum mechanics, there is no explanation for this. “It just comes out that way,” says theoretical physicist, Lee Smolin. Realists struggle with this because it would imply certain things can travel faster than light, which still seems improbable.