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Philosophers often distinguish between the primary qualities of objects, such as shape, size and motion, and their secondary qualities, such as colours, sounds and tastes.
One account of the distinction is this. Primary qualities are qualities of physical objects which resemble our perceptual experiences as of those qualities, whereas secondary qualities are qualities of physical objects which do not resemble our perceptual experiences as of those qualities. So squareness is a primary quality because it resembles our visual experience as of squareness. But redness is a secondary quality because there is no quality of objects which resembles our visual experience as of redness: the surfaces of objects are made up of collections of atoms which reflect light of certain wavelengths and not of others, and there is nothing in physical objects resembling our visual experience as of redness.
This way of making the distinction is open to two objections. The first is that it is unclear in what sense some experiences, but not others, resemble the qualities which they represent. What exactly is the notion of resemblance here? The second objection is that if the distinction between primary and secondary qualities is explained in terms of whether our experiences do, or do not, resemble the qualities of objects which they represent, then the distinction presupposes a representative theory of perception. It presupposes that our perceptual experiences of the qualities of objects are distinct from the qualities of objects we perceive. But many philosophers think the representative theory of perception unacceptable.
Another way of making the distinction between primary and secondary qualities avoids these problems. We can say that primary qualities are qualities of objects which (1) are represented by perceptual experiences and (2) figure in the correct explanation of such experiences. Squareness is a primary quality because it is represented by our perceptual experiences of certain objects and the correct explanation of why certain objects appear square to us is that they are square.
In contrast, secondary qualities are qualities of objects which (1) are represented by perceptual experiences and (2) do not figure in the correct explanation of such experiences. Thus, redness is a secondary quality because it is represented by our perceptual experiences of certain objects, and the correct explanation of why certain objects appear red to us is not that they are red, but that the atoms at their surface reflect light waves of a certain length, and these light waves cause us to have experiences as of red.
When philosophers say that redness is a secondary quality do they mean that things are not really red? Error theorists do. Error theorists maintain that when ordinary people clam that pillar boxes are red, they mean that redness figures in the correct explanation of why we have experiences as of red pillar boxes. Further, redness does not figure in the correct explanation of our experiences as of pillar boxes, so when ordinary people say that pillar boxes are red they are in error. Physical objects are not really coloured.
Other philosophers reject the error theory. Some hold a dispositional account of secondary qualities: secondary qualities are dispositions to produce certain sorts of experiences. Further, when ordinary folk say that pillar boxes are red, they only mean that pillar boxes are disposed to produce certain sorts of experiences as of redness. And pillar boxes are disposed to produce experiences as of redness, because they reflect light of a certain wavelength, and light of that wavelength causes experiences as of red in us. So physical objects are really coloured. AJ
See also representative theory of perception.Further reading C. McGinn, The Subjective View; , J.L. Mackie, Problems from Locke. |
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