Which belief system asserts that the natural world is filled with spirits?

The belief system that asserts the natural world is filled with spirits is animism. Animism is rooted in the idea that not only humans but also animals, plants, and inanimate objects possess a spiritual essence or soul. This belief is commonly found in many indigenous cultures around the world, where natural phenomena such as rivers, mountains, and trees are thought to have their own spirits or guardians.

In contrast, monotheism refers to the belief in a single deity, pantheism identifies God with the universe or nature itself, and polytheism is characterized by the worship of multiple gods. While pantheism and polytheism may involve a reverence for nature or its elements, they do not emphasize the presence of spirits in the same direct way as animism does. Thus, animism distinctly represents the understanding that various elements of the natural world are inhabited by spiritual entities.