George (1685–1753), Irish philosopher and bishop in the Anglican Church of Ireland, one of the three great British empiricists along with Locke and Hume. He developed novel and influential views on the visual perception of distance and size, and an idealist metaphysical system that he defended partly on the seemingly paradoxical ground that it was the best defense of common sense and safeguard against skepticism.
Berkeley studied at Trinity College, Dublin, from which he graduated at nineteen. He was elected to a fellowship at Trinity in 1707, and did the bulk of his philosophical writing between that year and 1713. He was made dean of Derry in 1724, following extensive traveling on the Continent; he spent the years 1728–32 in Rhode Island, waiting in vain for promised Crown funds to establish a college in Bermuda. He was made bishop of Cloyne, Ireland, in 1734, and he remained there as a cleric for nearly the remainder of his life.
Berkeley’s first major publication, the Essay Towards a New Theory of Vision (1709), is principally a work in the psychology of vision, though it has important philosophical presuppositions and implications. Berkeley’s theory of vision became something like the received view on the topic for nearly two hundred years and is a landmark work in the history of psychology. The work is devoted to three connected matters: how do we see, or visually estimate, the distances of objects from ourselves, the situation or place at which objects are located, and the magnitude of such objects?
Earlier views, such as those of Descartes, Malebranche, and Molyneux, are rejected on the ground that their answers to the above questions allow that a person can see the distance of an object without having first learned to correlate visual and other cues. This was supposedly done by a kind of natural geometry, a computation of the distance by determining the altitude of a triangle formed by light rays from the object and the line extending from one retina to the other. On the contrary, Berkeley holds that it is clear that seeing distance is something one learns to do through trial and error, mainly by correlating cues that suggest distance: the distinctness or confusion of the visual appearance; the feelings received when the eyes turn; and the sensations attending the straining of the eyes. None of these bears any necessary connection to distance. Berkeley infers from this account that a person born blind and later given sight would not be able to tell by sight alone the distances objects were from her, nor tell the difference between a sphere and a cube. He also argues that in visually estimating distance, one is really estimating which tangible ideas one would likely experience if one were to take steps to approach the object. Not that these tangible ideas are themselves necessarily connected to the visual appearances. Instead, Berkeley holds that tangible and visual ideas are entirely heterogeneous, i.e., they are numerically and specifically distinct. The latter is a philosophical consequence of Berkeley’s theory of vision, which is sharply at odds with a central doctrine of Locke’s Essay, namely, that some ideas are common to both sight and touch. Locke’s doctrines also receive a great deal of attention in the Principles of Human Knowledge (1710). Here Berkeley considers the doctrine of abstract general ideas, which he finds in Book III of Locke’s Essay. He argues against such ideas partly on the ground that we cannot engage in the process of abstraction, partly on the ground that some abstract ideas are impossible objects, and also on the ground that such ideas are not needed for either language learning or language use. These arguments are of fundamental importance for Berkeley, since he thinks that the doctrine of abstract ideas helps to support metaphysical realism, absolute space, absolute motion, and absolute time (Principles, 5, 100, 110–11), as well as the view that some ideas are common to sight and touch (New Theory, 123). All of these doctrines Berkeley holds to be mistaken, and the first is in direct conflict with his idealism. Hence, it is important for him to undermine any support these doctrines might receive from the abstract ideas thesis. Berkeleyan idealism is the view that the only existing entities are finite and infinite perceivers each of which is a spirit or mental substance, and entities that are perceived. Such a thesis implies that ordinary physical objects exist if and only if they are perceived, something Berkeley encapsulates in the esse est percipi principle: for all sensible objects, i.e., objects capable of being perceived, their being is to be perceived. He gives essentially two arguments for this thesis. First, he holds that every physical object is just a collection of sensible qualities, and that every sensible quality is an idea. So, physical objects are just collections of sensible ideas. No idea can exist unperceived, something everyone in the period would have granted. Hence, no physical object can exist unperceived. The second argument is the socalled master argument of Principles 22–24. There Berkeley argues that one cannot conceive a sensible object existing unperceived, because if one attempts to do this one must thereby conceive that very object. He concludes from this that no such object can exist ‘without the mind,’ that is, wholly unperceived.
Many of Berkeley’s opponents would have held instead that a physical object is best analyzed as a material substratum, in which some sensible qualities inhere. So Berkeley spends some effort arguing against material substrata or what he sometimes calls matter. His principal argument is that a sensible quality cannot inhere in matter, because a sensible quality is an idea, and surely an idea cannot exist except in a mind. This argument would be decisive if it were true that each sensible quality is an idea. Unfortunately, Berkeley gives no argument whatever for this contention in the Principles, and for that reason Berkeleyan idealism is not there well founded. Nor does the master argument fare much better, for there Berkeley seems to require a premise asserting that if an object is conceived, then that object is perceived. Yet such a premise is highly dubious.
Probably Berkeley realized that his case for idealism had not been successful, and certainly he was stung by the poor reception of the Principles. His next book, Three Dialogues Between Hylas and Philonous (1713), is aimed at rectifying these matters. There he argues at length for the thesis that each sensible quality is an idea. The master argument is repeated, but it is unnecessary if every sensible quality is an idea.
In the Dialogues Berkeley is also much concerned to combat skepticism and defend common sense. He argues that representative realism as held by Locke leads to skepticism regarding the external world and this, Berkeley thinks, helps to support atheism and free thinking in religion. He also argues, more directly, that representative realism is false. Such a thesis incorporates the claim that some sensible ideas represent real qualities in objects, the so-called primary qualities. But Berkeley argues that a sensible idea can be like nothing but another idea, and so ideas cannot represent qualities in objects. In this way, Berkeley eliminates one main support of skepticism, and to that extent helps to support the commonsensical idea that we gain knowledge of the existence and nature of ordinary physical objects by means of perception. Berkeley’s positive views in epistemology are usually interpreted as a version of foundationalism. That is, he is generally thought to have defended the view that beliefs about currently perceived ideas are basic beliefs, beliefs that are immediately and non-inferentially justified or that count as pieces of immediate knowledge, and that all other justified beliefs in contingent propositions are justified by being somehow based upon the basic beliefs. Indeed, such a foundationalist doctrine is often taken to help define empiricism, held in common by Locke, Berkeley, and Hume. But whatever the merits of such a view as an interpretation of Locke or Hume, it is not Berkeley’s theory. This is because he allows that perceivers often have immediate and noninferential justified beliefs, and knowledge, about physical objects. Hence, Berkeley accepts a version of foundationalism that allows for basic beliefs quite different from just beliefs about one’s currently perceived ideas. Indeed, he goes so far as to maintain that such physical object beliefs are often certain, something neither Locke nor Hume would accept. In arguing against the existence of matter, Berkeley also maintains that we literally have no coherent concept of such stuff because we cannot have any sensible idea of it. Parity of reasoning would seem to dictate that Berkeley should reject mental substance as well, thereby threatening his idealism from another quarter. Berkeley is sensitive to this line of reasoning, and replies that while we have no idea of the self, we do have some notion of the self, that is, some lessthan-complete concept. He argues that a person gains some immediate knowledge of the existence and nature of herself in a reflex act; that is, when she is perceiving something she is also conscious that something is engaging in this perception, and this is sufficient for knowledge of that perceiving entity. To complement his idealism, Berkeley worked out a version of scientific instrumentalism, both in the Principles and in a later Latin work, De Motu (1721), a doctrine that anticipates the views of Mach. In the Dialogues he tries to show how his idealism is consistent with the biblical account of the creation, and consistent as well with common sense.
Three later works of Berkeley’s gained him an enormous amount of attention.