George Berkeley was born in 1685 near Kilkenny, Ireland, to a family of English descent. In 1700 he entered Trinity College in Dublin where he studied languages, mathematics, and philosophy. In 1707 he became a fellow of the college, and in 1710 he was ordained into the Anglican Church. During the time of his studies Berkeley also traveled a great deal, and became acquainted with the work of Rene Descartes, Nicolas Malebranche, and John Locke. He was immediately impressed with these philosophers, but also deeply disturbed by their ideas. He found in the scientific views they put forth a lurking threat of skepticism and atheism, two forces that his life's work combated.
Berkeley published his first important philosophical work at the age of twenty- four, in 1709. This was his Essay Toward a New Theory of Vision. The book was well-received and a second edition came out later that same year. Encouraged by the success, Berkeley published A Treatise Concerning the Principles of Human Knowledge the following year, though to much less critical acclaim. The work was an attempt to lay out a complete philosophical system, on which the only existing entities in the world are ideas and the minds that conceive them. (He called his view "immaterialism", but it was later termed "idealism".) He considered this view to be the perfect antidote to skepticism and atheism. Very few people took these ideas seriously.
Despite the mockery he endured, Berkeley did not scrap his radical ideas. In 1713 he made another attempt to convince the world of the truth of his philosophical system, by putting his ideas into a more popularized form. The result of this effort, Three Dialogues Between Hylas and Philonous, was published in 1713 while Berkeley was living in London. Also while in London, Berkeley became acquainted with leading intellectual figures such as Joseph Addison, Alexander Pope, and Jonathan Swift. Ever-vigilant against the forces of skepticism and atheism he wrote several scathing articles attacking the theories of "freethinkers".
From 1713 to 1714 Berkeley traveled the continent, and probably met and spoke with Nicolas Malebranche. He took another traveling tour from 1716 to 1720. It was during this trip that he lost the manuscript for his second volume of the Principles. Unfortunately, he never rewrote it. He did, however, find the time to write a short Latin Essay entitled De Motu during this journey. In it, he criticizes Newton's philosophy of nature and Locke's theory of force, and he presents his own account of motion to supplant these.
In 1724 Berkeley was made dean of Derry, but he was already becoming disillusioned with the moral and spiritual decline he perceived in European culture, and had begun plans to found a new college in Bermuda. His intent was to establish an institution that would provide a solid education for the sons of American colonists, Indians, and Negroes (both from Bermuda and the mainland) in order to train these young men for the Christian ministry. In 1728 he departed for Rhode Island, with his new wife, in order to establish farms that would supply food to the college. He settled in Newport while awaiting the grant that he had secured from Parliament, but the grant never arrived. By 1731 it was clear that the money had been diverted to other purposes and Berkeley returned home. While in Newport, though, Berkeley carried on an interesting correspondence with Samuel Johnson, who was one of Berkeley's first defenders, as well as the future first president of Columbia University. Berkeley also wrote the Alciphron during this period, his meditation on religious conviction and attack on freethinkers.
He spent the years between 1732 and 1734 in London, primarily criticizing Newton, whom he called "an infidel mathematician" (though Newton himself was highly religious). In The Analyst and A Defense of Free-thinking in Mathematics Berkeley tried to undermine the authority of the mathematicians so admired by freethinkers, by revealing that the concepts they used were basically incoherent. In 1734 he was appointed Bishop of Cloyne, in Ireland. In this role he turned his attention to the health and wellbeing of his parishioners, mostly struggling country folk. He began to reflect on economic issues (giving rise to The Querist published in 1735) and, in the field of medicine, became convinced of the healing properties of tar water, to which he devoted his last philosophical work (entitled A Chain of Philosophical Reflections and Inquiries Concerning the Virtues of Tar Water, and published in 1744). He died nine years later in Oxford.
Despite the fact that Berkeley was at the forefront of one of the most outrageous trends in the history of philosophy (that is, idealism), he was actually a conservative; in fact, his radicalism grew out of his excessive conservatism. Faced with the freethinking 17th century scientists and writers who sought to overthrow traditional forms of religion, government, and conceptions of reality, Berkeley reacted by making a drastic philosophical move meant to prevent any further movement on these other fronts. By positing that the only things in the world are ideas and minds, Berkeley hoped to stem the threatening "freethinking" tide. As Berkeley himself succinctly puts it in the third dialogue, "That innovations in government and religion, are dangerous, and ought to be discountenanced, I freely own. But is there any like reason why they should be discouraged in philosophy?" (3.244)
By Berkeley's time a new science was in full swing, pioneered by thinkers like Descartes and Galileo, and now in the hands of men like Sir Isaac Newton and Robert Boyle. This new science was mechanistic and mathematical in nature; it sought to explain all physical phenomena in terms of the motion of tiny particles of matter. The entire physical world, on this view, was made up of these particles, or corpuscles, with nothing else added. Only certain extremists, such as Thomas Hobbes, actually believed that this picture gave an exhaustive description of the entire universe. Most thinkers of this age, including both Descartes and Locke, believed that in addition to the physical objects in the world (which could be explained in these purely mechanistic terms) there were also spiritual entities, or souls, both human, angelic, and divine (i.e. God). But while the dualistic view of Descartes and Locke opened up a space for God, souls, and all the other necessary trappings of religion, Berkeley felt that the space it left open was both too small and too precarious.
God, in this mechanical world, became almost superfluous; He was appealed to only now and then to close up certain gaps in the otherwise self-sufficient theories. (Descartes, for instance, uses God to provide force in his physical system, and Locke uses God to bridge the explanatory gap between the world as we experience it and the world as it really is.) Giving God these minor causal roles was not sufficient in Berkeley's eyes; to him it was clear that God had to entirely ground any true description of physical reality. In addition, he recognized that it was only a matter of time before the mechanistic philosophers closed all their gaps and eliminated God from their systems altogether. Philosophers such as Thomas Hobbes and Baruch Spinoza were already taking these last steps toward a godless science, either chasing God from their picture entirely or giving God such an abstract, impersonal form as to make Him unrecognizable to any religious believer. Berkeley was not the only religious believer to view the creeping atheism with fear. "The church in danger", was actually a popular war cry at the time. However, he did battle these forces with unusual vigor, and also probably came up with the most original means by which to proceed: banishing matter from the world altogether. It was for these efforts that he was made Dean of Derry, and then, ultimately, Bishop of Cloyne.
In order to understand how a conservative such as Bishop Berkeley could have been driven to posit a system as radical as idealism (and to have the gall to call this view "common sense") it is important to get a handle on two other philosophical systems of the era: the groundbreaking rationalism of Rene Descartes and the level-headed empiricism of John Locke.
Descartes, born in 1569, was not the first scientist to develop a mechanistic, mathematical science, though he was influential in its development, and perhaps most ambitious in his scope. He was, however, the first to give a thorough and comprehensive philosophical response to the demands raised by this new way of viewing the world. His writings initiated a dramatic revision of philosophical method and concerns. In order to clear the way for a new scientific outlook, Descartes had to dramatically simplify the metaphysical picture of the world. Where the Scholastics (the reigning leaders of the intellectual world at the time) had posited numerous types of substances, each with their own essence, and each requiring their own type of explanation in terms of earth, air, fire, and water, Descartes argued that there were only two types of substance in the world. There was mental substance, whose essence was thinking, and there was physical substance, whose essence was extension. Since the entire observable world thus reduced to a single sort of substance (i.e. physical substance or body), all natural phenomena could be explained by relying on just a small number of principles, based entirely on the property of extension. Physics conveniently collapsed into geometry, the study of extended body.
Given his mechanistic picture of the world, on which all explanation could be given in terms of the extension of physical substance, Descartes also needed a new epistemology, or theory of cognition, to complement his new physics and metaphysics. Scholastic philosophers, following Aristotle, believed that all human knowledge comes through the senses. That is to say, they were empiricists. However, their empiricism was of a very naïve form; they believed that our senses are incapable of systematically deceiving us about the kinds of things that are in the world. If the senses tell us that there are colors, then there are colors. If the senses tell us that there are enduring objects, such as tables and chairs, then there are enduring objects. The trustworthiness of the senses was built into the conception of how perception operated: the one perceiving, on this view, took on the form of the thing perceived, became, in a very obscure sense, like the object of perception. Yet on Descartes' metaphysical picture of the world, there was no such thing as color, sound, odor, taste, heat. There was only extension and the properties that arose from it, such as size, shape, and motion. In order to defend his physics and metaphysics, therefore, Descartes was forced to come up with a new understanding of where human knowledge comes from. Knowledge could not come from our senses, because our senses tell us that we live in a colorful, loud, odorous, tasty, hot, cold world.
In order to rid knowledge of sensory influence, Descartes' freed the intellect from the senses altogether. Where the Scholastics had claimed that nothing got into the intellect except through the senses, on Descartes' theory of cognition, certain concepts are present in the intellect at birth. According to Descartes, human beings are born with certain innate concepts, concepts such as "God", "extension", "triangle", and "something cannot come from nothing". Using these innate concepts, and our faculty of reason, we can trace chains of logical connections and unravel all the possible knowledge in the world.
Like Descartes, John Locke, was a proponent of the new science. He too believed that the natural world was explicable exclusively in terms of shape, size, and motion of matter, though the particulars of the view he ascribed to were somewhat different from the Cartesian picture. (Whereas Descartes believed that all matter was continuous, Locke ascribed to the chemist Robert Boyle's Corpuscular Hypothesis according to which the natural world is composed of indivisible bits of matter called corpuscles.) He had to admit, therefore, that Descartes was right about at least one thing: the senses do systematically deceive us. Locke, however, could not bring himself to accept Descartes' epistemology. Like the Scholastics, Locke believed firmly that nothing came into the mind without first coming through the senses. His work on epistemology and metaphysics(which can be found in the Essay Concerning Human Understanding, published in 1671, twenty years after Descartes' death), therefore, is an attempt to reconcile his empiricism with his commitment to the new science. His aim was to defend an empiricist model of the mind, while clearing the way for new ideas about the nature of reality.
The mixture of a Cartesian metaphysics and an empiricist epistemology, however, led Locke into many difficulties. According to the Cartesian metaphysics, the world as we experience it through our senses (that is, as colored, tasty, odorous, full of sound) is different from the way the world really is (that is, filled only with colorless, tasteless, scentless, soundless matter); but according to an empiricist epistemology, our only access to the world is through our senses. Taking this blend of ideas to its logical conclusion, then, Locke's philosophy seems to lead straight into skepticism: we cannot know what the world is really like; we cannot know the true nature of things. Only adding to the force of this skeptical conclusion is Locke's theory of perception, also taken over from Descartes. According to this theory, we do not have immediate access to the world, but, rather, we see the world through an intermediate layer of ideas, often referred to as the "veil of perception". In other words, objects in the world cause ideas to spring up in our mind, and it is these ideas, and not the objects themselves, that we see when we look out around us. But if we have no immediate access to the world, one might reasonably ask, how on earth do we know if our ideas resemble what is really out there? Descartes was able to get around this worry, by claiming that we can know about the world through our purely intellectual, innate ideas, but Locke, as an empiricist, could not use this escape hatch. His philosophical system, then, not only leads to the worry, "can we know about the true nature of things", it also leads to the worry that, for all we know, the world as it is, is nothing like the world as we experience it. The entire world could actually be, say, one giant, undifferentiated ball of jello (with no objects, bodies, etc. in the mix), and we would be none the wiser.
Locke himself strenuously resisted any skeptical conclusions. In fact, he did not even take the threat of skepticism seriously. Berkeley, however, did take this threat seriously, and he viewed the Lockean mixture of Cartesian metaphysics and empiricist epistemology with a deep suspicion. As a committed empiricist himself, Berkeley needed to find a way to avoid the skeptical conclusions that Locke's philosophy seemed to lead to. His solution was to scrap half of the Cartesian metaphysics, eliminating matter and keeping only mind. By claiming that all there is in the world is ideas and the minds that perceive them, Berkeley was able to avoid the worries that crept up for Locke. The world, on this view, must really be colored, tasty, smelly etc. because the world just is our ideas. Therefore, we can also be certain that we know the true nature of things. In addition, there is no veil of perception on Berkeley's picture, because the ideas to which we have immediate access are the real objects out in the world; there is nothing coming between us and really existing things. We never have to worry, then, that reality does not correspond to our perception of it; we know what exists out there, and what it is like.
Though Berkeley's solution might sound ludicrous (it certainly did to all of his contemporaries) it actually ended up becoming widely influential. In the 19th century, idealism became all the rage, beginning with Kant (who denied he was an idealist, but came close enough to be called one by most people since) and culminating in Hegel, Schelling, and the British Idealists like Greene, Bosanquet, Bradley, and Andrew Seth. Though these philosophers tended to denigrate Berkeley's importance, they owed their most fundamental ideas to his innovations, and even based their own arguments on ones that he himself had made two centuries earlier.