John Locke on primary and secondary qualities:

"Such qualities, which in truth are nothing in the objects themselves, but powers to produce various sensations in us by their primary qualities, i.e. by the bulk, figure, texture, and motion of their insensible parts, as colors, sounds, tastes,etc., these I call secondary qualitites" John Locke

Popular Works:

• An Essay Concerning Human Understanding
• Two Treatises of Government

Born 1632, in Wrington, Somerset, England. John Locke lived through politically and religiously turbulent times. He witnesses the English Civil War of the 1640s, the abolition of the monarchy, the House of Lords and the Anglican Church, and then saw the restoration of all three after Oliver Cromwell's death in 1658. In the early 1680s Locke fled to the Netherlands when susptected of plotting against James II of England, returning only after the Glorious Revolution which forced James to flee to France and be replaced by William of Orange, the Dutch Ruler. Locke returned in style--aboard the royal yacht, with William III's wife and co-monarch, Mary II, elder daughter of the deposed James.

Locke's political philosophy has been immensely significant. As a social contract theorist, he defended the right of the citizens to revolt against a government that rules without their consent. His thinking influended the founding fathers of the United States, and their drawing up of the American Declaration of Independence. He is considered to be the first of the British empericist philosophers. He died 1704, in Oates, Essex.

I'm focusing on two of John Locke's major works in this hub. Both of these works illustrate his philosophy on primary and secondary qualities. In An Essay Concerning Human Undestanding, Locke aims to find the limits of human understanding. He defends empiricism, arguing that all knowledge, and indeed all concepts, are ultimately derived from experience.

Locke rejects the rationalist docrinte of innate ideas defended, for example, by Rene Descartes, insisting instead that the mind at birth is a tabula rasa--a blank slate. Locke's Essay also sets out and defends one of the clearest and most sophisiticated versions of the distinction between primary and secondary qualities. It is on that distinction that we focus here.

The majority of philosophers interpret Locke as holding a version of the representational theory of perception, whereby we do not perceive the world around us directly. As an empiricist, Locke insists that our access to the world is provided by our five senses: sight, hearing, smell, taste and touch. However, this access is not direct--as if we were looking through an open window. Rather, what each of us is immediately aware of is akin to an inner mental image or representation that, in effect, stands between us and the world. Locke calls these inner mental entities that mediate perception ideas.

This is an example he uses. I see you throw me a red apple, which I reach out and catch. According to Locke, as the apple approaches, it produces in my mind a string of ideas, including ideas of red, a round shape increasing in size, and so on. These ideas inform me that the apple is nearing. Reaching out and catching the apple produces further auditory and tactile ideas. When I sniff and bite into the apple, that results in ideas of smell and taste.

If Locke is correct, I never actually get to experience the apple or, indeed, any physical object, directly. All perception of the external world is mediated by ideas.

Locke asks--when I perceive the world via these ideas, to what extent is what I perceive independently there? What contribution does my mind make to what I experience of the world around me? It is in answering this question that Locke's version of the distinction between primary and secondary qualities comes into play.

According to Locke, colors, smells, tastes and sounds are not, in truth, fully objective qualities of external physical objects. Rather they consist in the powers or dispositions that those physical objects have in producing certain ideas in us.

In order to understand Locke's thinking, we should begin by looking at some other examples of dispositional qualities. Take, for example, the qualities of being fragile or highly flammable is just for it to be true that if it were exposed to naked flame, then it would burn easily. Similarly, for something to be fragile is just for it to be true that if knocked sharply, then it would break.

Notice that, in order for a vase to be fragile, it need never actually break. It merely has to be true that it would break were it sharply knocked. A dispositional quality consists of the fact that something would happen, if the circumstances were right. It need not actually happen.

Locke's view is that colors, tastes and smells are also dispositional qualities. For something to be red is just for it to be true that if we were to look at it, then it would then produce in our minds a certain sort of visual experience or idea.

So Locke agrees that things are red even when no one is looking at them. A red flower growing in some remote alpine meadow is still red even if no one ever sees it growing there. And yet, if Locke is right, the color will remain essentially mind-dependent. It remains the case that for the flower to be red is just for it to be true that if we were to look at it, then we would have certain idea.

To bring out the contribution Locke supposes the mind makes to color, let's consider some hypothetical beings whose minds are very different to our own. Suppose there are aliens whose minds are very different from our own. Suppose there are aliens whose nervous systems are put together very differently, so that when they look at the world, it appears to them as a color negative appears to us. When they look at grass, it produces in them the kind of color experience that poppies produce in humans, and vice versa.

What color is grass, from the point of view of these aliens? The answer, from Locke's view, is red. It is not that the aliens mistakenly think that grass is red. No-for the aliens, the grass really is red. For the aliens, grass has the power to produce in them the idea of red.

In short: Locke's theory of color makes relative to the minds of perceivers. For beings with minds like ours, poppies are red, sugar is sweet and garbage smells disgusting. But it's possible that, for beings with different sorts of mind, poppies are green, sugar is sour and garbage smells fragrant. There is no 'objective fact of the matter' as to what colors, smells and fragrances thing really possess. All these qualities are, in truth, mind-dependent.

Locke calls those qualities that consist in the powers or dispositions of objects to produce particular ideas in us secondary qualities. He supposes that tastes, smells and colors are all secondary qualities.

But if tastes, smells and colors are mind-dependent qualities, which qualities are primary? Which aren't mind-dependent?

Roundness, according to Locke, is a primary quality. This apple is both red and round. Its redness consists in a power of the apple to produce a certain idea in us. That is not true of its roundness. True, this apple has the power or disposition to produce the idea of roundness in us. When I look at, it looks round. However, though the object possesses that power, its being round does not consist in that power. The apple would still be round even if, for some bizarre reason, it happened to look square.

According to Locke, shape, size, number and position are all examples of primary qualitites. They are fully mind-independent qualities of material objects, possessed independently of hwo those objects might happen to strike us.

Interestingly, Locke offers a second definition of primary and secondary qualities--a definition that makes use of the notion of resemblance. According to Locke, our ideas of primary qualities resemble those qualities as they are in an object. But that is not true of our ideas of secondary qualities. There is nothing resembling my idea of red on the surface of this red apple.

Locke embraced the 'corpuscular' theory of matter popular with scientists of the time--a theory in which physical objects were thought to be composed of tiny insensible corpuscles or parts. For Locke, these microscopic particles possess only primary qualities. A physical object such as an apple is ultimately nothing more than a vast collection of corpuscles. It is the microscopic arrangement of these corpuscles that determines how the object will impinge on our sensory organs, and so cause ideas in us.

So according to Locke, when it comes to shape, size, number, motion and the other primary qualities, appearances are not fundamentally misleading. Physical objects really do possess length, breadth, position and number and move around in space, in much the way they seem to. But when it comes to colors, smells, and tastes, appearances are deceptive. There is, in truth, nothing like my idea of sweetness in a spoonful of sugar. Ultimately, all there is 'out there' are the tiny corpuscles jiggling about in the void.

Although the distinction between primary and secondary qualities was not new (Boyle, Galileo and Descartes had already made it), Locke's version is clearer and more sophisticated. But is the theory correct? Are colors, tastes and smells mind-dependent in the way Locke claims them to be? It's one thing to claim that these qualities are secondary, but it's quite another to show that they are. There is some arguments that support this theory.

Perhaps the most popular argument for colors, tastes and smells being secondary qualities is that scientists make little use of these qualities when formatting scientific laws and offering scientific explanations. Scientists appeal to lengths (such as wavelengths), position (such as position of an electron landing on a screen) and motion (such as motion of a particle) in order to explain why things behave in the way they do. Rarely do they appeal to the smell or taste or color of a thing (certainly not when it comes to the most fundamental explanations). It seems that secondary qualities are explanatorily superfluous--their role in accounting for how things stand in mind-independent reality is redundant. But if taste, smell and color are redundant in the explanation of how matters stand in reality doesn't that suggest that they aren't, in truth, part of that reality? Doesn't it suggest that they are, after all, mere secondary qualities?

I leave you to judge. If you have anything to add I welcome your comments. Thanks for taking the time to read--I hope there was something contained here that you had not previously known.