Ideas, experience and a material world

A cup on the table

Imagine Leah turning a green cup in her hands. Its glaze catches the light, and its warmth reaches her fingers. Seen from above, the rim looks round; at an angle, it looks oval. She puts the cup down and leaves the room, expecting it to remain.

What does her experience reveal about the thing she was holding? The previous lesson asked what can count as a substance, and John Locke and George Berkeley approach that question through our experience of ordinary objects. Both give experience a central role, yet they disagree about whether material substance helps explain it. Empiricism names a family of approaches that give experience this importance, and its members disagree about what experience warrants us in believing.

Where ideas come from

In Locke’s Essay Concerning Human Understanding, an idea is what the mind is occupied with in perceiving or thinking. The term covers a taste, a shape, our awareness of doubting and a complex thought alike; it does not simply mean a visual image. [1]

Locke traces the materials of thought to two sources. Sensation supplies ideas through our senses. Reflection supplies them when we notice our own mental activity: remembering, comparing, choosing, doubting. When Leah feels warmth and notices herself wondering whether the tea is still hot, she has one experience of each kind.

The mind also works on what it receives. A simple idea, such as a particular taste, cannot be broken into further ideas; the mind combines such materials into complex ideas, compares them and rearranges them. So it receives the materials of thought without remaining passive in everything it does with them. Our idea of a cup can include its warmth and feel as well as its look, much of which a photograph would leave out.

The object and its powers

Locke distinguishes an idea in the mind from the quality of the object that produces it. The cup’s power to produce a sensation of warmth is not itself the felt warmth. [1]

Primary qualities, such as solidity, extension (occupying space), shape and motion or rest, belong to bodies whether or not anyone perceives them. Secondary qualities are powers, grounded in the arrangement and motion of a body’s minute parts, to produce sensations such as colors, tastes and warmth. Calling greenness a secondary quality does not mean that Leah invents it at will. The cup has a power to affect her under suitable conditions.

Locke holds that our ideas of primary qualities resemble qualities in bodies, while our ideas of secondary qualities do not resemble their causes. That already rules out a theory on which every sensation is a faithful internal picture. It also raises a question: what entitles us to say that some ideas resemble a reality independent of perception?

What bears the qualities?

Leah treats the cup’s features as belonging to one thing. For Locke, our idea of a particular substance combines its qualities with the supposition of something that supports them. Substratum names that supposed underlying support. It is not merely another visible layer beneath the green glaze, since whatever supported that layer’s qualities would raise the same question again. [1]

Locke admits that we have no clear idea of this support considered in itself: we meet the qualities together without clearly understanding what bears them. He treats that admission as a limit on our understanding, not as reason enough to deny that bodies exist. Berkeley asks whether the supposed support has any intelligible work left to do.

Berkeley’s challenge

Berkeley starts from what we perceive: colors, shapes, resistance, warmth and other ideas. Several of them regularly occur together, and we call the collection a cup. An idea exists in being perceived. So if the cup is this collection of sensible ideas, its existence cannot be independent of every perceiving mind. This is the crucial step to examine. [2]

Could these ideas instead copy a material original outside any mind? Berkeley replies that an idea can resemble only another idea. A perceived color can resemble another perceived color, but how could it resemble something that cannot be perceived at all? He extends the challenge to shape and motion, so primary qualities receive no automatic exemption.

The changing appearance of Leah’s rim adds pressure. The shape we see varies with our viewpoint, just as other sensible appearances vary with conditions. But Berkeley himself acknowledges that this kind of argument does not by itself prove that an external quality is absent; it challenges only our knowledge of which appearance represents the quality correctly. His stronger conclusion depends on the earlier argument about ideas and their possible originals.

A defender of material objects can therefore ask whether Berkeley has identified the object too quickly with what is immediately perceived, or demanded too narrow a kind of resemblance. Berkeley presses a question in return: how does merely naming an unknown support explain the experience? The dispute concerns the reasoning that leads from experience to what exists.

The cup remains real

Berkeley’s immaterialism denies that there is any mind-independent material substance. It keeps cups, tables and other ordinary objects, understood as sensible things, along with active perceiving spirits. Ideas are passive; minds perceive and will. Leah, then, is not another item in the collection she calls a cup. [2]

Nor can she turn warm tea cold just by imagining it. Berkeley distinguishes the steady, coherent ideas of sense from the less regular products of imagination. Because sensory ideas do not obey our will, he argues, another spirit must produce them, and he explains their ordered course through God’s activity. This inference relies on his earlier account of spirit as the source of activity.

So the cup’s existence does not depend on Leah’s attention alone. Berkeley distinguishes being unperceived by me from being independent of all minds, and his account invokes an eternal spirit. One can question that account while recognizing that he means to preserve the reality of ordinary life.

Try the explanation

Leah says, “My cup looks different from different angles, so Locke must think its shape is imaginary. Berkeley goes further and says the cup is unreal.” Repair both claims, then name one premise Berkeley needs beyond changing appearances. This exercise is optional.

Read a possible response

Both claims misread their targets. For Locke, shape is a primary quality that belongs to a body whether or not we perceive it, so a change in how the rim looks neither makes its shape imaginary nor shows that every appearance represents it correctly. Berkeley, for his part, keeps the real cup: it is a stable collection of sensible ideas, not something Leah invents at will, and what he rejects is an unperceiving material substance behind those ideas. His argument needs more than variation: for example, the premise that an idea can resemble only another idea, together with his account of what we perceive. Challenging that premise would engage the argument more directly than pointing out that we can still drink from cups.

Carry this forward

Keep two questions apart: where our ideas come from, and what their presence warrants us in claiming. Agreeing that experience matters need not settle the second. Habit, causation and the self asks what experience gives us when one event repeatedly follows another: do we perceive a necessary connection, or come to expect one?

Sources and limits

[1] John Locke, An Essay Concerning Humane Understanding, volume I, Books I–II, Project Gutenberg eBook 10615, for ideas, qualities and substance. The Project Gutenberg catalogue describes a text based on the second edition; the electronic title page carries 1690. Read II.i.1–5, II.ii.1–3, II.viii.7–26, II.xii.1–6 and II.xxiii.1–6 and 37. A locator such as II.viii.15 means Book II, chapter eight, section fifteen.

In II.viii, §§14–15 and 23 supply the distinction used here; the text supplied at II.viii.10 is only an omission notice, not a paragraph read. The opening of II.xxiii lacks its section-one label. The transcription has apparent errors, and no comparison with a printed edition was made. No complete reading of the Essay is claimed.

[2] George Berkeley, A Treatise Concerning the Principles of Human Knowledge, University of Oregon, Renascence Editions, 1999 electronic presentation, derived from an ERIS Project text through an Adelaide mirror, for Berkeley’s challenge and his immaterialism. Read the Preface and main-text §§1–20, 25–36, 45 and 48:

• Resemblance and primary qualities: §§8–10.
• The limit of the argument from variation: §15.
• Spirits, experience and ordinary objects: §§25–36.
• Perception beyond one’s own mind: §§6 and 48.

The work first appeared in 1710. This transcription does not identify its underlying print edition, and no comparison of the 1710 and 1734 editions was made.

Both sources are English texts, not translations. Sources accessed 18 September 2026. Leah and the cup are original teaching material. No independent scholarly review, learner testing or measured reading time is claimed.