George Berkeley

George Berkeley (12 March 1685 – 14 January 1753), also known as Bishop Berkeley, was an Irish philosopher, and one of the three most famous British Empiricists (with John Locke and David Hume). He is best known for developing an early form of idealism, according to which the only things which exist are minds and the ideas which they perceive. The University of California, Berkeley, and the city that grew up around it were both named after him.

"Philosophy being nothing else but the study of wisdom and truth, it may with reason be expected that those who have spent most time and pains in it should enjoy a greater calm and serenity of mind, a greater clearness and evidence of knowledge, and be less disturbed with doubts and difficulties than other men. Yet so it is, we see the illiterate bulk of mankind that walk the high-road of plain common sense, and are governed by the dictates of nature, for the most part easy and undisturbed. To them nothing that is familiar appears unaccountable or difficult to comprehend. They complain not of any want of evidence in their senses, and are out of all danger of becoming Sceptics. But no sooner do we depart from sense and instinct to follow the light of a superior principle, to reason, meditate, and reflect on the nature of things, but a thousand scruples spring up in our minds concerning those things which before we seemed fully to comprehend. Prejudices and errors of sense do from all parts discover themselves to our view; and, endeavouring to correct these by reason, we are insensibly drawn into uncouth paradoxes, difficulties, and inconsistencies, which multiply and grow upon us as we advance in speculation, till at length, having wandered through many intricate mazes, we find ourselves just where we were, or, which is worse, sit down in a forlorn Scepticism." From 'A Treatise Concerning the Principles of Human Knowledge' (1710).

Vision

In An Essay towards a New Theory of Vision (1709) Berkeley set out an empirical theory of vision which challenged Descartes' account of distance vision, an account which requires geometrical calculations based on the disparity between images formed in two eyes set apart. The size of the retinal image of an object is smaller the further away that an object is, yet we do not perceive a similar change in the size of an object as it recedes - we perceive it as being of a constant size. Descartes had proposed that we constantly implicitly calculate the true size of the object by estimating its distance from us, and correcting for that - and proposed that we implicitly estimate the distance of an object by measuring the disparity of the retinal images in our two eyes. By contrast, Berkeley argued that we estimate the size of an object by using our past experience - by associating the image with what we know of the size of the object, and by our experience for example that distant things appear fainter than near things. He argued that the distance, magnitude, and shape of objects are properties which are directly perceived only by touch, so to ascribe these properties to things that we see, we must learn to associate ideas of sight and touch. This associative approach explained how distance vision can be achieved with only one eye, and the moon illusion, anomalies unexplained by the geometric account.

Berkeleyan idealism

"But, say you, surely there is nothing easier than for me to imagine trees, for instance, in a park [. . .] and nobody by to perceive them. [...] The objects of sense exist only when they are perceived; the trees therefore are in the garden [. . .] no longer than while there is somebody by to perceive them."

The central thesis of Berkeley's idealism was that only minds and the ideas which they perceive exist. This committed him to immaterialism, the position that there are no material substances, where a substance is something which could exist even if nothing else did. According to Berkeley, objects like trees and chairs existed, but they could not exist independently of being perceived by a mind. He summarised this position with his famous dictum, "Esse est percipi" ("To be is to be perceived").

This thesis has been commonly expressed as "If a tree falls in a forest and no one is there to hear it, does it make a sound?" Berkeley's ultimate answer to this was that there is always a mind that perceives it - the mind of God.

Berkeley and infinitesimals

"Thus Fluxions may be considered in sundry Lights and Shapes, which seem all equally difficult to conceive. And indeed, as it is impossible to conceive Velocity without time or space, without either finite length or finite Duration, [ ] it must seem above the powers of Men to comprehend even the first Fluxions. And if the first are incomprehensible, what shall we say of the second and third Fluxions, &c.? He who can conceive the beginning of a beginning, or the end of an end, somewhat before the first or after the last, may be perhaps sharpsighted enough to conceive these things. But most Men will, I believe, find it impossible to understand them in any sense whatever."

In 1734 Bishop Berkeley published a tract called The Analyst. In this, the new calculus of Newton and Leibniz was attacked and especially the concept of "fixed infinitesimal" set forth by Isaac Newton in the Principia and in an appendix to the Opticks. Since the concept of an infinitely small, and yet finite, quantity was still fairly muddled and confused, Berkeley, although not a mathematician by training, made an extremely effective attack. His arguments provoked controversy among mathematicians and led to the clarification of central ideas underlying the new theory.

External links

• Berkeley’s central arguments for immaterialism, PhilosoFiles