Locke’s Claim That Secondary Qualities Are Not in Objects Themselves: A Deep Dive into Empiricist Epistemology
John Locke’s Essay Concerning Human Understanding presents a revolutionary distinction that reshaped philosophy’s understanding of reality. Practically speaking, this doctrine challenges our intuitive perception of the world and forms a cornerstone of empiricist thought. At its heart lies his claim regarding secondary qualities—a thesis asserting that these qualities, such as color, taste, sound, and odor, do not reside intrinsically in objects but are instead powers to produce sensations in us. Understanding Locke’s argument requires examining his broader theory of ideas, the critical difference between primary and secondary qualities, and the philosophical and scientific motivations behind his radical claim.
It sounds simple, but the gap is usually here.
The Foundational Distinction: Primary vs. Secondary Qualities
Locke’s entire discussion rests on a fundamental classification of the attributes we perceive in objects. This division is not merely scientific but epistemological, concerning how we acquire ideas.
Primary Qualities are those that are “utterly inseparable” from the body, no matter what state it is in. They exist objectively in the object itself and are discoverable through careful observation and measurement. Locke’s list includes:
- Bulk, figure, texture, and motion of parts.
- Number (when considered in relation to the object’s parts).
- Solidity or impenetrability.
For Locke, a piece of wax retains its primary qualities—its extension, shape, and the motion of its minute parts—even when it melts, changes color, or loses its scent. These qualities are independent of any observer.
Secondary Qualities, on the other hand, are defined by their relational nature. They are “nothing in the objects themselves but powers to produce various sensations in us.” This means:
- They depend on the primary qualities of an object’s insensible parts (its corpuscles).
- Their effect is to trigger a sensory response in a perceiver.
- The sensation (e.g., the experience of red) is in the mind of the observer, not in the object.
Locke’s classic examples include:
- Colors (red, blue)
- Sounds (sweet, harsh)
- Tastes (sweet, bitter)
- Smells (fragrant, foul)
- Temperatures (hot, cold—in the sense of the feeling of heat)
Crucially, Locke argues that if a body is divided into its minute, insensible parts, it no longer possesses secondary qualities. And a grain of wheat, when ground into dust, no longer tastes sweet or looks yellow. The sweetness and yellowness were not in the ultimate corpuscles themselves but were powers those corpuscles had, when assembled in a certain way, to affect our senses Most people skip this — try not to..
Locke’s Argument: Why He Denies Secondary Qualities to Objects
Locke’s argument is not based on mere speculation but on careful reflection on the nature of perception and the limits of human understanding. His reasoning can be broken down into several key points:
1. The Argument from Variability: Our senses often give us conflicting reports about the same object. A single object can appear yellow to one person, or not yellow to a person with jaundice; water that feels warm to a cold hand feels cold to a hot hand. If the quality (yellowness, warmth) were really in the object, it could not be both present and absent simultaneously. That's why, the quality must be something projected by the perceiver’s condition, not an intrinsic feature of the object Not complicated — just consistent..
2. The Argument from the Insensible Corpuscle: Locke, following the emerging mechanical philosophy of Boyle and Newton, posits that material objects are composed of minute, inert corpuscles in motion. These corpuscles have only primary qualities. If we could see the world at this micro-level, we would see only bulk, figure, and motion. The secondary qualities—the redness, the sweetness—are not visible at this level. They must therefore be the result of the interaction between the primary qualities of the object and the sensory organs of the perceiver. The object has the power to cause a certain idea in us, but the idea itself is not a copy of anything in the object.
3. The Argument from Explanatory Power: The mechanical philosophy sought to explain all natural phenomena in terms of matter in motion. Explaining why sugar tastes sweet is more coherent if we say the spherical shape of its particles interacts with our taste buds to produce a sweet sensation, rather than saying sweetness is an invisible, immaterial property actually inhabiting the sugar. Attributing secondary qualities to objects adds an unnecessary and inexplicable layer to our scientific ontology.
4. The Argument from Analogy with Pain: Locke draws an analogy with the sensation of pain. We do not say that a sword contains pain; we say it has a power to cause pain when it cuts us. Similarly, a fire is not hot in the sense that it possesses a “hotness” substance; it has the power to cause the sensation of heat in us. This analogy powerfully illustrates the mind-dependent nature of sensory qualities Not complicated — just consistent. Worth knowing..
The Scientific and Philosophical Context: A Paradigm Shift
Locke’s claim was a direct response to the scientific revolution. Still, earlier scholastic philosophy often treated sensory qualities as real, objective properties. Galileo and Descartes, however, argued that only quantifiable, mathematical properties (like shape and motion) were truly real in the physical world. On the flip side, locke sought a middle ground. Now, he agreed with the new science that the fundamental nature of matter was mechanical and mathematical, but he wanted to preserve the reality of the sensory world for us. His solution was the distinction between primary and secondary qualities. The primary qualities are what science describes; the secondary qualities are the effects those primary qualities have on our sensory equipment. This allowed Locke to be both a modern scientist and a defender of common sense experience.
Short version: it depends. Long version — keep reading Simple, but easy to overlook..
Common Objections and Locke’s Potential Replies
Objection 1: It leads to skepticism. If the red I see isn’t in the rose, is the rose not red at all? Locke would reply that the rose is certainly red in our experience. The quality “red” exists as a sensation in us when we perceive a normal rose under normal conditions. The rose’s reality is not diminished; it is simply understood correctly as having the power to produce that experience Which is the point..
Objection 2: It makes secondary qualities purely subjective. Doesn’t this mean beauty is “in the eye of the beholder”? Locke would concede that the experience is subjective, but the power to produce that experience is an objective fact about the object’s microstructure. A ripe strawberry has an objective, molecular structure that regularly produces sweet sensations in human beings with normal biology. The subjectivity lies in the sensation, not in the causal power Still holds up..
Objection 3: The distinction is unclear. Where exactly is the line? Locke acknowledges the difficulty but insists the core distinction holds. Some qualities, like solidity, seem to blur the line, but he maintains that primary qualities are those that explain the object’s behavior in the mechanical world, while secondary qualities explain our sensory interaction with it.
The Lasting Legacy and Significance
Locke’s doctrine of secondary qualities is more than a historical footnote; it is a living idea that continues to influence philosophy of mind, philosophy of science, and even cognitive science. It directly paved the way for:
- Berkeley’s Idealism: If secondary qualities are mind-dependent, what grounds
Locke’s framework remains a cornerstone, bridging empirical observation with philosophical inquiry, its ripples echoing through disciplines that seek to unify knowledge and reality. Now, such synthesis underscores the layered dance between objectivity and subjectivity, a theme that continues to challenge and inspire scholarly pursuits. In this context, understanding persists as a testament to the enduring interplay of thought and experience.
Conclusion: Thus, Locke’s contributions illuminate the complexities of human understanding, bridging past and present while inviting ongoing exploration. His legacy endures not merely as historical context but as a guiding principle, reminding us of the foundational role science and philosophy play in shaping our grasp of existence itself.
