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 A Treatise Concerning the Principles of Human Knowledge, claiming that the only substances were immaterial /.
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.
- George Berkeley (1710)[minds.http://philosophy.eserver.org/berkeley.html 'A Treatise Concerning the Principles of Human Knowledge']