TOV / Philosophy

George Berkeley versus John Locke

Does reality exist independently of a perceiving mind?

George Berkeley's famous Latin formula, esse est percipi, meaning “to be is to be perceived,” captures the central claim of his immaterialism. Berkeley challenged the assumption that ordinary objects depend on a material substance existing independently of any mind. In doing so, he confronted the philosophy of John Locke, whose empiricism had helped establish the terms of the debate.

Their disagreement reaches beyond the question of how human beings perceive a tree or a table. It concerns the limits of knowledge, the existence of an external world, and the place of God in explanations of reality. Both men were committed Christians, but they developed strikingly different accounts of what our experience permits us to know.

What Berkeley Meant

Objects and perception

Berkeley did not deny that tables, chairs, and trees are real. He denied that they consist of an independently existing material substance behind the colors, shapes, textures, and other qualities we experience. An ordinary object, on his account, is an orderly collection of sensible ideas perceived by a mind.¹

For Berkeley, sensible things exist insofar as they are perceived. The familiar question about a tree in an unobserved forest therefore raises no threat to its continuity: even when no human or animal perceives it, its existence is secured by the infinite mind of God. This does not mean that the tree is a hallucination. Berkeley regarded the stable, involuntary experiences of the world as genuinely real.

The role of God

We cannot simply decide what we will see when we open our eyes. Nor can we freely rearrange the regularities of nature by imagination. Berkeley argued that these orderly sensory experiences have a cause beyond our finite wills: God, an infinite spirit who produces our sensory ideas according to dependable laws.

His universe consists of active spirits, which perceive and will, and passive ideas, which are perceived. There is no third category of mind-independent material substance. Berkeley's system is therefore immaterialist, although it still distinguishes spirits from the ideas they experience.

A religious philosophical project

Berkeley was an ordained Anglican clergyman who became Bishop of Cloyne in 1734. His philosophical arguments were closely tied to his religious commitments. He believed that theories of matter existing independently of all minds encouraged skepticism and weakened recognition of divine activity. By making God fundamental to the regularity and continuity of experience, he sought to defend both ordinary knowledge and Christian belief.

How Berkeley Challenged John Locke

Locke, a major figure in British empiricism, argued that our ideas arise from experience, through sensation and reflection. He accepted an external material world whose objects possess qualities that help produce our sensory ideas. Berkeley adopted much of Locke's starting point but questioned whether Locke was entitled to infer a material reality lying behind those ideas.

Their disagreement centered on the distinction between primary and secondary qualities and the problem of the material substance supposedly underlying the properties of objects.

The Battle over Qualities

Locke distinguished primary qualities, such as solidity, extension, shape, motion, and number, from secondary qualities, such as colors, tastes, sounds, and smells. Primary qualities belong to objects whether anyone perceives them or not. Secondary qualities are powers in objects to produce particular sensations in perceivers.²

An apple, for example, possesses physical properties that produce the experience of redness under suitable lighting and perceptual conditions. The sensation of red occurs in the observer, although the capacity to produce it depends on the apple and its physical environment.

Berkeley's counterargument

Berkeley challenged the distinction. Whenever we imagine a shape, we imagine it as possessing some sensible presentation. We cannot encounter shape in perception independently of all the sensory qualities through which it appears. If color and other secondary qualities are mind-dependent, Berkeley reasoned, the allegedly independent primary qualities cannot be cleanly separated from them.

His objection is powerful as a criticism of what can be immediately perceived. Yet it is not a conclusive proof about what exists beyond perception. The difficulty of imagining a colorless or otherwise unperceived shape does not itself demonstrate that spatial properties cannot exist independently of a mind. The argument moves from a limitation on experience or conceivability to a claim about the nature of reality.

The Veil of Perception and Material Substance

Locke's account is frequently described as representative realism. We are immediately aware of ideas, while those ideas provide our knowledge of objects existing independently of us. This arrangement creates a philosophical problem often called the veil of perception: how can we establish that our ideas accurately represent a world we do not encounter without their mediation?

In An Essay Concerning Human Understanding (1690), Locke begins his account of ideas by observing:

“Every man being conscious to himself that he thinks; and that which his mind is applied about whilst thinking being the ideas that are there...”³

The passage illustrates Locke's understanding of ideas as the immediate objects of thought. His broader account also acknowledges a difficulty in explaining the underlying substance that supports the qualities we perceive. Locke famously characterizes this supposed support as “something, I know not what.”³

Berkeley's counterargument

Berkeley considered this unknowable material substratum unnecessary. If experience gives us only ideas, what warrants the additional assumption of matter existing beyond all possible perception? Berkeley proposed eliminating that assumption and treating sensible objects as real ideas whose order and persistence ultimately depend upon God.

This reasoning has an economy reminiscent of the principle commonly called Occam's razor: do not multiply explanatory entities without necessity. Berkeley believed his approach removed an important source of skeptical doubt. It did not, however, eliminate every possible question about perception or the justification of his theological premises.

Two Christian Philosophers, Two Accounts of Nature

Both Locke and Berkeley were religious thinkers who regarded reason and Christian belief as compatible. Locke was no simple advocate of a deity who creates a clockwork universe and then abandons it. He defended the rational examination of religious claims and accepted providence, revelation, and miracles. Berkeley likewise defended Christianity, but made continuous divine causation central to his understanding of sensory experience.

Divine creation and continuous divine causation

Locke accepted a material world created by God, ordered by natural laws, and accessible to human understanding through experience. Berkeley rejected the independently existing material substance presupposed by this explanation. What we call the laws of nature are, for Berkeley, the regular ways God causes sensory ideas in finite minds. Nature becomes an intelligible language through which divine order is expressed.

Reason and revelation

Locke was particularly suspicious of religious enthusiasm, the conviction that one possesses divine truth without sufficient rational grounds. He argued that claims of revelation should be assessed in the light of reason. Berkeley was more willing to build explicitly theological conclusions into an account of perception, though he too intended his position to rest on philosophical argument rather than unexamined faith.

Berkeley's Central Irony: The Return of an Invisible Substance

Berkeley's most revealing difficulty arises from the very standard he applies to Locke. He objects that Locke cannot justify an imperceptible material substance supposedly supporting the properties we experience. Yet Berkeley's own explanation depends upon spirits: active beings that are themselves not objects of sensory perception. Most consequentially, the stability of the entire sensible world depends upon an infinite divine spirit.

Berkeley recognized this objection. In A Treatise Concerning the Principles of Human Knowledge, §§139–140, he distinguishes an idea from a notion. We have sensory ideas of colors, sounds, and shapes, but we do not have a sensory idea of a spirit. Instead, Berkeley argues, we understand spirit through our awareness of ourselves as beings who think, perceive, and will. The perceiver is not another perceived object.¹

This distinction is philosophically significant. Berkeley is not simply contradicting himself by admitting an unseen entity after rejecting another. His defense is that the notion of an active mind has intelligible content grounded in our own mental activity, whereas Locke's unknown material substratum lacks a comparably clear explanation.

Nevertheless, the defense leaves a serious problem. First-person awareness that thinking occurs does not establish the independent existence of an immaterial substance that performs the thinking. Even if a finite spirit can be understood through self-awareness, it does not follow that an infinite spirit exists or continuously produces every regular sensory experience. Berkeley's account of God goes substantially beyond the experience from which his empiricism begins.

His attack on material substance raises a legitimate question: why assume more than experience and reason warrant? The same question can be directed toward his immaterialism. If the inability to perceive material substance counts against Locke, Berkeley must explain why an unperceived divine spirit deserves a different evidentiary standard. His notion of spirit is an attempted answer, but whether it succeeds remains contested.⁴

Philosophical Differences at a Glance