In Locke's discussion of names of mixed modes and names of substances in EHU 3.5-6, he seems to suggest that the ideas of mixed modes are in some way more arbitrary than the ideas of substances. Some commentators, such as Nicholas Jolley (Locke: His Philosophical Thought, 155-161), have found this claim problematic for, according to Locke, ideas of substances are 'the workmanship of the understanding'; they are not given to us by nature.
I think, however, that considerations from book two are sufficient to answer this worry. Locke defines mixed modes as "such Combinations of simple Ideas, as are not looked upon to be the characteristical Marks of any real Beings that have a steady existence, but scatted and independent Ideas, put together by the Mind" (2.22.1). Ideas of substances are introduced as follows:
The Mind being ... furnished with a great number of simple Ideas, conveyed in by the Senses, as they are found in exteriour things, or by Reflection on its own Operations, takes notice also, that a certain number of these simple Ideas go constantly together; which being presumed to belong to one thing ... are called so united in one subject, by one name" (2.23.1).
What this suggests is that the difference between ideas of substances and ideas of mixed modes is one of direction of fit: when coming up with a new idea of a mixed mode, one first stipulates a definition, then asks whether anything satisfies it. When coming up with a new idea of a substance, one inspects an object or set of objects and tries to come up with a collection of ideas which will be useful as part of a classificatory scheme for that object or set of objects. The object or set of objects is an archetype to which the idea will be compared, because the idea is intended to describe it. The idea may be false, since one may be mistaken about the qualities of the object. The idea will necessarily be inadequate since there will always be more qualities which are not included in one's idea. This last is assured because Locke holds that phenomenal qualities follow from the 'secret natures' or 'real essences' of things which are utterly inaccessible to us, so any objects which have known qualities in common also have unknown qualities in common.
This distinction is well-illustrated by Locke's two stories about Adam:
Let us suppose Adam in the State of a grown Man, with a good Understanding, but in a strange Country, with all Things new and unknown about him; and no other Faculties, to attain the Knowledge of them, but what one of this Age has now. He observes Lamech more melancholy than usual, and imagines it to be from a suspicion he has of his Wife Adah (whom he most ardently loved) that she had too much Kindness for another Man. Adam. discourses these his Thoughts to Eve, and desires her to take care that Adah commit not folly: And in these Discourses with Eve, he amkes use of these two new Words, Kinneah and Niouph. In time, Adam's mistake appears, for he finds Lamech's Trouble proceeded from having kill'd a Man: But yet the two Names, Kinneah and Niouph; the one standing for suspicion, in a Husband, of his Wife's Disloyalty to him, and the other, for the Act of Committing Disloyalty, lost not their distinct significations.
One of Adam's Children, roving in the Mountains, lights on a glittering Substance, which pleases his Eye; Home he carries it to Adam, who, upon considerations of it, finds it to be hard, to have a bright yellow Colour, and an exceeding great weight. These, perhaps at first, are all the Qualities, he takes notice of in it, and abstracting this complex Idea, consisting of a Substance having that peculiar bright Yellowness, and a Weight very great in proportion to its Bulk, he gives it the Name Zabah, to denominate and mark all Substances, that have these sensible Qualities in them (3.6.44, 46)
The first story is meant to illustrate the introduction of mixed mode terms, and the second of substance terms. In the first story, Adam constructs an idea (the idea of adultery) and wonders whether anything satisfies it. (It is notable that Locke intentionally constructs the case in such a way that it is uncertain whether such a thing has ever occurred.) Adam's idea serves as the archetype to which the things in the world are compared. In the second story, Adam has a sample of gold before him and observes its qualities and incorporates those into an idea meant to "mark all Substances, that have these sensible Qualities in them." The sample of gold serves as an archetype, and the idea is constructed by observing it.
This also helps to explain why Locke's examples often contain terms that are partially normative (Jolley, pp. 158-159): we hold normative concepts fixed and try to ensure that the world conforms or does not conform to them. Purely descriptive concepts are typically not like this.
There is an odd case that Locke's theory, on my interpretation, has difficulty accounting for. This is the case of theoretical posits. Take the planet Neptune, for example. Wikipedia doesn't seem to say when exactly Neptune was named, but it does say that Neptune was postulated to explain irregularities in the orbit of Uranus before it was observed directly. Suppose, for the sake of argument, that before direct observation of Neptune someone had said, "let us use 'Neptune' as a name for a planet which causes the irregularities in the orbit of Uranus." Astronomers then attempt to determine by empirical investigation whether anything in the world matches this description. According to my interpretation of Locke, under these circumstances 'Neptune' would be a name of a mixed mode. Of course, since language is conventional, once Neptune was observed directly, the meaning of 'Neptune' could be changed so that it became a (proper) name of a substance. As a result, I think this slight weirdness might not be so bad.Posted by Kenny at June 14, 2010 5:32 PM
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