George Berkeley was a famous and well respected Irish philosopher during the 18th century. In his classic works, he championed the idea of "immaterialism", arguing that physical objects are only physical because they are perceived as such by living beings. Included are the following: 1.A Treatise Concerning the Principles of Human Knowledge 2.An Essay Towards a New Theory of Vision 3.Three Dialogues between Hylas and Philonous In Opposition to Sceptics and Atheists 4.The Querist, Containing Several Queries Proposed to the Consideration of the Public 5.A Defence of Free-Thinking in Mathematics