Locke on the world and how we perceive it (23-Oct-2003)

Reading : Western Philosophy II.4 "Qualities and Ideas"

The Locke scholar Michael Ayers says: "The great achievement of 17th Century philosophy was the assimilation of the truth that now seems axiomatic to most of us, that fundamental explanations in science cannot start from the natures or essences of complicated physical objects such as are large enough to be perceived."

Locke was working at a similar time to Robert Boyle, who formulates "Boyle's law", and was influenced by the idea of corpuscularianism: that all matter is composed of minute, insensible (i.e. we can't sense them) particles.

In a similar vein to Descartes, Locke sees substances as being fundamental, and says that we perceive them by virtue of their attributes, or qualities. For Locke, a quality is an aspect of an object that is responsible for evoking a particular response in us which he calls an idea.

Locke categorises qualities as being either primary or secondary. The two differ in two ways:

  1. the ideas produced by primary qualities in some way resemble the property of the quality in question. So primary qualities (which Locke lists as solidity, extension, figure (shape), motion and number) are perceived by us in a way that more or less accurately reflects something about the object. Secondary qualities (including colour, taste, smell) on the other hand, produce ideas in us which are purely subjective experiences and are not "in" the object at all.
  2. While primary qualities in some way reflect some true aspect of the object, secondary qualities "depend on those primary qualities" - that is, they are no more than by-products of the primary qualities which already exist

If we consider a banana, we have an idea of its shape which resembles the true shape of the banana. But the yellow colour that we experience and attribute to the fruit is (a) a purely subjective emotional experience that doesn't exist in the fruit, and (b) no more than a function of the primary qualities of the particles which make up the banana (e.g. we only see the colour yellow because the molecules in the skin are laid out in such a way as to reflect certain frequencies of light wave).

Locke's ideas seem to resonate with what we know of the physical world today: many of the subjective ideas that he mentions are explicable in terms of the way that the individual particles of a substance move about and bounce off our sense organs.

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