Immaterialism

Immaterialism is the position that there are no material substances. It is a form of the philosophical theory known as idealism. Its most famous advocate was George Berkeley, an 18th century Irish philosopher who defended it in works such as The Principles of Human Knowledge, claiming that the only substances were immaterial minds.

Immaterialism is sometimes misunderstood as the position that ordinary objects like trees and stones do not exist. For example, on hearing of Berkeley's theory, Samuel Johnson famously kicked a stone and remarked: "I refute it thus!" `However, Berkeley did not deny that objects like stones existed, but merely denied that they were substances, suggesting instead that they were collections of ideas.