Berkeley’s Idealism

One way to construe the contrary claim that the world is mind-dependent is to take seriously traditional idealism. On this view, what exists is mental, and hence mind-dependent: it cannot exist without the mind.

Now, ‘idea’ is a technical term in Berkeleyan philosophy (Principles §§38-39). Calling something a thing has a connotation of existing without the mind. In this sense, ideas are not things. They cannot exist unperceived or without the mind. The sensible qualities of ‘things’ are ideas—hence the ‘things’ are collections of sen­sible qualities which are called ideas. Significantly, ideas are “the objects of sense”—to sense is to perceive; hence what one perceives is an idea. This technical use of the term ‘idea’ removes the paradox that is usually associated with idealism: after all, we are fed with food and not with ideas. As Berkeley put it: “we are fed and clothed with those things which we perceive immediately by our senses. The hardness or softness, the colour, taste, warmth, figure, and such like qualities, which combined together constitute the several sorts of victuals and apparel, have been shown to exist only in the mind that perceives them”. Given that there are only two kinds of Being, “spirits and ideas”, everything is mental. Spirits “are active, indi­visible substances”; ideas “are inert, fleeting, dependent beings, which subsist not by themselves but are supported by, or exist in, minds or spiritual substances”.

Berkeley, notably, intended to make his idealism consistent with corpusculari- anism—which posited invisible corpuscles.^[67] But corpuscles, if they exist at all, must be ideas (collections of ideas, to be sure); hence they require minds or spiritual substances “to exist in”. Yet, they are not ideas (or collections thereof) that are imprinted on our own senses. They can only exist in the spirit that perceives them, and this can only be God.^[68] So, plausibly, corpuscles ‘exist in’ God; they are dependent on him. Hence corpuscles are OK-Berkeleyan entities since they cannot exist without the mind. For Berkeley it is enough for something to exist to be perceived by “the eternal mind of the Creator”.

But in this sense, corpuscles can be deemed “‘external’ with regard to their origin” (§90) in that the relevant ideas are “not generated from within the mind itself” (meaning: the human mind); they can also be deemed to exist “without the mind” in the sense that they [the corpuscles] “exist in some other mind”, viz., God’s mind.

Berkeley does not deny that unthinking things are in some sense real. But he’s careful to note that, according to him, “the unthinking beings perceived by sense, have no existence distinct from being perceived, and cannot therefore exist in any other substance, than those unextended, indivisible substances, or spirits, which act, and think, and perceive them” (Principles §91). The ideas that are excited in minds “from the outside” have law-like connections. They are impressed “according to certain rules or laws of nature, speak themselves the effects of a mind more pow­erful and wise than human spirits”. These ideas, then, are not “fictions of the mind”. They are not produced “at pleasure”. In fact, the ideas that are produced “from the outside”, that is sensations, “are said to have more reality in them than the former [ideas excited by the mind “from the inside”]. Hence, the sun is real—that it, when we perceive the sun, we perceive the “real sun” (Principles §36).

In the sense here given of ‘reality', it is evident that every vegetable, star, mineral, and in general each part of the mundane system, is as much a real being by our principles as by any other. Whether others mean any thing by the term ‘reality' different from what I do, I entreat them to look into their own thoughts and see (Principles §36).

The key point here is that for idealism reality (including reality which is not directly sensed by the human senses, like invisible corpuscles) is mind-dependent because it is mental: it is either mental substances (spirits) or mental attributes (which cannot exist without the mental substances). Hence, mind-dependence should be understood as a claim about what exists, that is about what kinds of stuff make up reality.

In light of the distinction drawn in the Introduction, Berkeley's reality is mind-dependent because Berkeley denies the irreducible existence of things and posits that insofar as they are taken to be (in some sense) real, they are so because they are reducible to collections of another type of (mental) entity, viz. ideas. Interestingly, Berkeley's position vis-a-vis the objectivity condition is a bit more complex. Insofar as the existence of things (qua reducible to ideas) and in partic­ular, the existence of invisible mechanisms, is not tied to them being sensed by human minds, that is, insofar as he denies that they are collections of ideas pos­sessed by humans, Berkeley allows that what exists is not tied to a humanly realisable epistemic condition, to wit perceivability. But from this it does not follow that they exist objectively since for something to exist it must be perceivable by God even if it is not perceived by humans. Hence, Berkeley comes to compromise the second sense in which reality is mind-independent. For Berkeley there is simply no way in which there might be a divergence between what God (being a supreme mind) knows and what there is.

Though there are important arguments against idealism—going back to G E Moore among other philosophers—my main point here is not that idealism is wrong.^[69] My main point is that even though it is consistent with idealism that there are unperceived-by-humans entities and even though an idealist, pretty much like a scientific realist, could believe in the existence of electrons and their ilk, scientific realism is anti-idealism and, by the same token, idealism is inconsistent with scientific realism.

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