Appendix 35.
(902) [Primary and secondary qualities]
Reid glimpsed this truth when he posited the difference between the primary and secondary qualities of bodies. He saw that the primary qualities give us distinct notions, the secondary, confused notions. His observation is true but he was unable to explain it. To the question whether the distinction is real, he replies:
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I answer, That there appears to me to be a real foundation for the distinction; and it is this - that our senses give us a direct notion of the primary qualities, and inform us of what they are in themselves. But of the secondary qualities, our sense give s only a relative and obscure notion - they inform us only, that they are qualities that affect us in a certain manner - that is, produce in us a certain sensation; but as to what they are in themselves, our senses leave us in the dark. |
For Locke, the distinction between the primary and secondary qualities lies in this: primary qualities, and certainly not the secondary, are likenesses of bodies. Reid completely rejected this opinion of Locke. He might not have done so if he had carefully noted the true principle from which the distinction between the primary and secondary qualities of matter must be drawn. According to this principle, sensation is composed of two parts, one subjective, the other extrasubjective. As we have seen, the extrasubjective element is the perception of the primary qualities, which are truly extrasubjective. From this point of view we can say that sensation is a likeness of the external agents because it has in common with them the qualities of multiplicity and continuity; having common qualities is the same as having likeness. Here I agree with Locke's opinion which, however, I limit and explain. In fact I believe that pyrrhonism relative to sensible things is inevitable when all likeness between bodies and sensations is rejected. Moreover, there could be no reply to Bayle's objections about primary qualities. All his objections arise from his failure to observe the extrasubjectivity of primary qualities, and his consequent attempt to make them subjective like other qualities.