George Berkeley (1685-1753) is most famous for his provocative claim that material objects don’t really exist. Positively, he claimed that “to be is to be perceived”. Berkeley took as a starting point the view of Descartes and Locke that perceptions are “ideas” in the mind, but took issue with the further assumption of Descartes and Locke that ideas nonetheless also “represent” things that exist independent of the mind. It seems to me that the implicit concept of mind in this kind of usage assumes way too much, but for now I won’t dwell on that.
Berkeley has been the subject of superficial ridicule as a poster child for extreme subjectivism, but that is a caricature. Famously, he is supposed to have maintained, e.g., that a tree falling in the woods and heard by no one makes no sound. As 20th century analytic philosophers have noted, however, even if his positions are ultimately untenable, the quality of his arguments is actually quite high. Apart from the abstract “metaphysical” question of the actual existence of external objects, he also generally wanted to vindicate common sense.
Far from denying the existence of any objective reality, what he really wanted to do was articulate an alternate account of objectivity, based on something other than the independent existence of discrete objects. He had two different kinds of responses on the falling tree. One invokes counterfactual conditions; all that is of practical relevance to us are the conditions under which a perception would occur. The other invokes God as a universal witness.
From within the tradition of British empiricism, Berkeley partially anticipates the non-representationalist accounts of objectivity developed by Kant and Hegel, using the resources of a kind of Christian Platonism. Unlike Kant and Hegel, he flatly asserts that what really exists are what he calls spirits, which combine Christian-Platonic attributes with those of minds in a broadly Cartesian-Lockean sense.
A bit like the monads of Leibniz but without the infinite nesting and mutual inclusion Leibniz posited, Berkeley’s spirits are inherently active, and inherently endowed with perception. Spirits have experience that is expressed in purely immanent and immediate — but entirely passive and inert — contentful ideas.
Berkeley wrote an important early work on the theory of vision, arguing that what we really see is immediate phenomena of light and color, rather than inferred “things”. This was an important source for phenomenalism in early 20th century philosophy of science. Like the later phenomenalists, he tried to explain all cognitive error as bad inference from good immediate perception. From this point of view, “ideas” cannot be wrong, because they are purely immediate and purely inert; the possibility of error depends on the actions of finite spirits.
The common tradition of Cartesianism and British empiricism insists that there is a layer of immediate apprehension that is immune to error, and wants to ground knowledge and science by more authentically getting back to that immediate layer. I think Kant and Hegel convincingly showed that everything we experience as immediate actually has a prehistory, so that immediacy itself is only an appearance, and all immediacy that we experience is really what Hegel called mediated immediacy. Mediated immediacy has the same general kind of explanation as what is called “habit” in translations of Aristotle. We “just know” how to ride a bicycle once we have already learned. We don’t have to think about it; we just spontaneously do it. Similarly, I think “immediate” perception involves a complex unconscious application of categories that is affected by large bodies of previous experience.
Thus I want to say that there is no layer of human experience that is immune to error. On the other hand, through reflection and well-rounded judgment, we genuinely but fallibly participate in objectivity. Objectivity is not something that is simply “out there”; it is a real but always finite and relative achievement.