“Esse est percipi” (“To be is to be perceived”) — A Treatise Concerning the Principles of Human Knowledge.
The Anglo-Irish philosopher Berkeley, is renowned for his propounding of idealism, based on the principles of empiricism. Idealism is a dogma which states that our reality is only mentally constructed; predicated on our mind and ideas. Berkeley’s belief in idealism would manifest itself following John Locke’s proposal of causal realism, which asserts that one can establish an external world’s existence. Locke argued that all worldly objects consisted of both primary and secondary qualities. Primary qualities being characteristics objects possess, separate from the observer (i.e. shape, size et cetera). Secondary qualities being the qualities of objects contingent on the observer (i.e. sound, smell, taste et cetera).
Berkeley rejected Locke’s idea of causal realism, arguing that “extension, figure, and motion are only ideas existing in the mind, and […] an idea can be like nothing but another idea”. For example, an A4 sheet of paper is doubtlessly a rectangle, yet, once turned 45°, it becomes a rombus. In addition, Berkeley contended that causal realism did not go hand in hand with empiricism, due to the progressive chain, beginning with the observed external object, and ending with the secondary qualities perceived. Since we are unable to differ our experience whilst awake or asleep, Berkeley ascertained this meant that the causal link was nonexistent. Berkeley hereby denied the presence of matter. Yet, he did not believe that objects both appeared and disappeared out of thin air, arguing that God had omnipresent vision, and it is through this, that objects keep existing.
Berkeley, George, and Colin M. Turbayne. A Treatise concerning the Principles of Human Knowledge: With Critical Essays. Indianapolis, NY: Bobbs-Merrill, 1977. Print.