Born in Kilkenny, Ireland, George Berkeley (1685-1753) was educated at Oxford, spent several years in Italy and America, and served for 18 years as the Anglican Bishop of Cloyne, Ireland.
In psychology, he is best known for his work on vision, his emphasis on associations and his belief that complex perceptions are composed of simple mental elements. In philosophy, he founded idealism and challenged Newton’s concepts of time and space. In 1866, Berkeley, California was named in his honor.
Berkeley’s 1709 book on vision explained how we perceive 3 dimensions with eyes which can only see in two dimensions. According to Berkeley, we perceive depth by associating the convergence of the eyes with other sensations (e.g., the size of an object is smaller as distance increases). His interest in perception also tied to Berkeley’s philosophy. He maintained that perception is the essence of being. In an attempt to counter what he perceived to be attacks on God, Berkeley proposed an imaginative argument against dualism and materialism.
Materialists reasoned that matter is all that exists so God cannot exist. Dualists maintained that this world is a bad copy of a separate world of ideas. Berkeley started with the premise that God exists and argued that without Him nothing would exist. Berkeley’s argument rested on 2 premises: (a) nothing can be perceived without a mind and (b) there are things the human mind can’t perceive. His conclusion was that there must be a mind that perceives everything seen and unseen: God. It is not so much that we perceive therefore we are (to paraphrase Descartes) but that we are, therefore someone is perceiving us. Although Berkeley’s philosophy was not widely accepted, his criticism of materialism and dualism founded a new approach called idealism.
For more on this topic, here’s a video on the Mind-Body Problem.