Berkeley, George (1685-1753)
Home: Kilkenny, Ireland
School: Founder of the modern school of Idealism, created to reject Locke's materialist philosophy, in order to support the existence of God. Idealism would hold that matter does not exist independent of the mind - a concept that eerily predates modern physics' quantum and indeterminacy theories - it may be that Berkeley uncovered the most profound and counterintuitive discovery in the history simply by rational examination, although his motivations may questioned. (Only God could qualify as the universal observer who is required to constantly call all matter into existence.) - he was, after all, a Bishop.)
Rational/Empirical: Empiricist/Idealist. He also followed the laws of contiguity/ associationism -experience. Despite Berkeley's views on matter, he is an empiricist of the first order for his acceptance that knowledge should be derived from the senses.
Greatest achievement: Empirical observations on perceptions. Preview of Quantum Physics of Indeterminism, with his view that nothing exists until observed. This concept was considered ludicrous in his time. Today it may be the only real accurate reading of reality.
Significant Works: The Principles of Human Knowledge, The Three Dialogues -. His contemporaries regarded both statements of his philosophy as foolish.

Berkeley is an unusual theorist, because much of what he says eerily predates modern quantum theory and even superstring theory. For example, superstring theory says that all matter is really just the movement of a super string that exists in 10 dimensional space - i.e. matter does not exist in the manner that our senses believe it to exist. Let's examine what he has to say

First, Berkeley was a philosopher on a mission. He recognized that the materialists were making great strides towards eliminating the necessity of the "god hypothesis". And if they could ever get to the point that matter could be seen as existing independently, they might get to a point where they were able to show that it did not need any creator.

So, Berkeley was out to make sure that god did not suffer the indiginity of being disproven by some materialists. He cleverly decided that the best course of action was to show that not only did matter need a god, not only that it couldn't exist independently of him, but that it didn't exist at all! Once he did this, then, from this negative proposition it would not be very tough to show the existence, nay, the necessity of god.

"To be is to be perceived"
- Bishop Berkeley
Berkely made that famous statement in reaction to the skepticism and agnosticism of philosophers such as Locke. Bishop Berkeley believed that Locke assumed too much when he proposed that matter had some independent existence apart from the mind. Berkeley held that matter cannot be conceived to exist independent of the mind.

For those who have read Orwell's 1984, this philosophy is NOT akin to how O'Brien viewed matter in Orwell's "1984." As William James points out, Berkeley was not denying the existence of matter , or claiming that we were free to think whatever we wanted about matter (as O'Brien's claimed). This is how Betrand Russell describes Berkeley's view:

When you see a tree, Berkeley points out that what you really know is not an external object, but a modification of yourself, a sensation, or as he calls it, and idea. This, which is all that you directly know, ceases if you shut your eyes. Whatever you can perceive is in your mind, not an external material object. Matter, therefore, is an unnecessary hypothesis. What is real about the tree is the perceptions of those who are supposed to "see" it; the rest is a piece of unnecessary metaphysics
Betrand Russell, Unpopular Essays, "Philosophy's ulterior motives" pg 60.
This phenomena of sense which Russell explains for us so well, has a problem with it, in that all matter can only continue on in existence while it is perceived, a problem that Berkeley himself saw as folly - since he supposed that things must have some permanency. Therefore, all of matter can be explained only by supposing a deity that continually perceives the universe. (A "God's eye view" that views all things from all directions at all times.) Berkeley's philosophical system eliminated any possibility of knowledge of an external material world - because observation itself created it.

Today quantum theory argues that this observer effect of creating reality can work BACKWARDS, so making unnecessary a god - man himself, after the fact, could have called the universe into existence by observation. (To use the lingo, he could have collapsed the "wave function" of quasi universes into one real universe.)

In arguing against Locke, Berkeley agreed with Locke in that only what is perceived is known, yet held that only Locke's secondary perceptions existed, since matter could not exist independent of the mind. Objects were merely aggregations of sensations, leading to an associative theory of learning.

Berkeley's empirical work on visual perception was of importance because it illustrated that complex perceptions could be understood as compounds of elementary sensations such as sight, hearing and touch, gained from experience. (Convergence/divergence of eyes), and not some innate form, such as Descartes geometry theory of distance vision.

Bishop Berkeley destroyed this world in one volume octavo; and nothing remained, after his time, but mind; which experienced a similar fate from the hand of Mr. Hume in 1737.
- Sydney Smith (1771-1845), English writer, clergyman. Sketches of Moral Philosophy, Introduction (1850).