Why do philosophical realists argue that objects can exist independently of human thought?

Philosophical realists argue that objects exist independently of human thought based on a fundamental distinction between "mental" and "physical" entities. While mental entities—such as thoughts, pains, or headaches—are private and depend on a mind to exist, physical objects—such as tables, rocks, and planets—are considered "public" and mind-independent.1

To a realist, the existence of a physical object is not affected by whether it is being perceived or experienced by anyone. This perspective is central to realism, which defines itself by the belief that the things we perceive possess a nature or existence that remains constant regardless of human cognition.12

Realists often contrast this view with idealism, which asserts that reality is composed exclusively of ideas or mental states. By maintaining that physical objects exist "out there" in the world, realists seek to account for the objective, public nature of our environment, even when faced with the challenge of explaining how we gain knowledge of these objects through private sensory experiences.31