Principles of Human Knowledge (Commonly called "Treatise" when referring to Berkeley's works) is a 1710 work by the Irish Empiricist philosopher George Berkeley. This book largely seeks to refute the claims made by his contemporary John Locke about the nature of human perception. Whilst, like all the Empiricist philosophers, both Locke and Berkeley agreed that there was an outside world, and it was this world which caused the ideas one has within one's mind; Berkeley sought to prove that outside world was also composed solely of ideas. Berkeley did this by suggesting that "Ideas can only resemble Ideas" - the mental ideas that we possessed could only resemble other ideas (not physical objects) and thus the external world consisted not of physical form, but rather ideas. This world was given logic and regularity by some other force, which Berkeley did his best to conclude was a God. Long refuted by most philosophers, Berkeley's claims are often felt to have been a form of rationalization - Berkeley later became Bishop of Cloyne, and was a highly religious man. Treatise's suggestion that the world was made of ideas with an omnipotent force guiding was his alternative to the Lockean Empiricism popular at the time, which Berkeley felt led to skepticism. In spite of this Berkeley was a capable, respected and entertaining thinker. Some doubt exists as to whether he truly believed his conclusion that the world at large was composed of ideas; with modern thinking tending towards him indeed having thought this to be the case.