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Primary and Secondary qualities by John Locke

  1. Aug 22, 2008 #1
    Is this another one of John Locke's bad ideas (like the human mind as a "sheet of paper") or am I missing something here?


    That entry is brief and explains it well:

    Primary qualities exist and are independent of any observor, such as the shape of a table.

    Secondary qualities exist and are produced by the sensation of the observor, such as the color of the table.

    So, primary qualities are in bodies, the secondary qualities are in the percipient. So, without eyes there are no colors, without ears there is no sound, and so on.

    But, don't things such as sound, light, color and so on have properties that are measurable? For instance, our perception of color depends on the arrangement of the electrons and protons of the object and so on, not just psychological factors. You can even tell some properties of things such as fire by its color. I guess this wouldn't apply to people who are color blind, which might support Locke's position, but there is a chance he could utilize science to help "understand" color.

    There are some quotes on the wiki page saying that these properties wouldn't exist if living beings didn't exist to observe them. I believe the same case could be made that nothing exists if we didn't observe them. And, as Berkeley points out, as noted in the classic "History of Western Philosophy," many of these same properties exist to primary qualities, meaning they depend upon the observer as well. No two people would see the "shape" of the table exactly the same way, etc.
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  3. Aug 22, 2008 #2
    The nature of many of the above mentioned things were not known at the time when John Locke made his theories. What he was trying to do was distinguish between things that are universally constant from those that vary based on the bias of the observer. For example, a marathon runner might describe a short path as being 50 miles. A rather spherically shaped person typing out philosophical posts on a physics forum might describe an epic journey as being 50 miles. The distance is objective and can be measured as 50 miles in both cases. How people perceive the distance as either a "short path" or an "epic journey" is subjective.

    It is easy to see in Locke's time why he would have grouped sound and color (both poorly understood at the time) into the subjective realm. A older man might hear differently than a younger man and both would hear more than a deaf man. A colorblind man might not see green compared to someone who wasn't color blind and both would see more than a completely blind man, etc. So, since the phenomena are perceived differently by different people, couldn't we say that these things are subjective? The flaw in the logic is that we now know that it is differences in the ability of sensory organs themselves (and not in the phenomena triggering the sensory organs, which can be the same in all of the above cases) that can cause someone to see or hear things in different ways. It is a triumph of science that we can now understand and even detect things such as sound and color whether our inbuilt sensory organs allow us to or not (as in the older man who can now hear more things with the hearing aide to amplify the existing sound).
  4. Aug 22, 2008 #3


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    At the same time, what is "color" to the human mind is differen than what is "color" to a dog or fish or CCD camera. The colors we see are totally constructed by the human mind.

    A person with red/green color blindness can't see the colors red and green.....or can they? Actually, they can - they just see them differently than "normal" people do.

    So I'd say he's absolutely correct about that example.
  5. Aug 22, 2008 #4


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    Hi OrbitalPower,
    “secondary qualities” are also called “qualia”. The first time you come to understand this strange situation is always confusing, but yea . . . I’m afraid you’re missing something here. Locke’s correct. Qualia in fact, are one of the most talked about and poorly understood facts about congitive science. Just as the Wiki article states, such things as color, sound, taste, etc… are things we as human experience but that don’t exist independent from us. The shape of something on the other hand, exists independent of an observer. We can safely assume an apple still has the shape it does when no one is looking, but it NEVER has color – it only refects certain wavelengths of light which correspond to what humans perceive as color. It isn’t the apple that has color. Color is a phenomena (qualia or “secondary quality”) which is created by a brain.

    It might help to consider philosophical zombies (p-zombies). A p-zombie is a conceptual person who doesn’t experience the color red and doesn’t in fact have ANY experience or qualia. Imagine talking with someone who acts and behaves exactly as if they are able to see colors, experience pain and pleasure, hear things, yet they are as dead inside as a rock. Such people would have no sensation when looking at a red apple, though they could tell you it was red because the wavelength of light the p-zombie measured equated to what humans call ‘red’. So as the article is saying, color is not a measurable property, wavelength is. Sound is not a measurable property, the pressure waves in air are. The light wavelengths exist and the pressure waves exist independantly of a human. But color and sound are constructs of the human (or other animal’s) brain and otherwise do not exist.
  6. Aug 22, 2008 #5
    Right. And a person who is completely deaf wouldn't hear a loud boom that I would hear at all.

    Does that mean the sound waves don't exist? I agree with Renge Ishyo; the primary and secondary qualities might have been applicable at the time, and a good theory at the time, but by today's standards they are largely out of date.

    Furthermore, you could make the argument that if all life doesn't exist then certainly things like "shapes" do not exist just as easily imho.


    Here, I'm afraid I just simply disagree. The shape of an object is not "independent of the observor," it also depends upon the arrangement of atoms and so on and humans can easily be fooled by what looks like a smooth object is actually quite rough, even by human standards at times.

    Of course, the shape does ultimately exist in a certain form, but how we observe it also depends on our perception, and so you could give that same argument about shape as Berkeley notes.

    I would say sound certainly would have an effect on the natural world if their were no human beings because other species would still hear them, and react. Even if they weren't there the sound waves still exist.

    I'm in the "if a tree falls in a woods and no one hears it it still makes a sound" group I guess.

    I agree with most of what you said, but Berkeley was able to debunk it by applying the same standards of secondary qualities to primary qualities.
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