Là-bas… Les merveilleux nuages!

The American Midwest doesn’t do mountains or oceans. One thing it does do is clouds. This evening as I sat in the bay window on the second floor, looking northwest, the setting sun played off a cumulus cloud set against a background of thin cirrus. The trailing, western edge was pink and reddish-orange; the bulk of the cloud was grey, gradually darkening toward the east. A cloud thus illuminated has relief, it gains mass, becomes, however temporarily, a thing. Now the sun has set and the wind has taken it east, out of sight—across the river, perhaps.
You don’t need wind to make a cloud disappear. You can banish it with logic, using the sorites paradox.
The standard example is this:
If a thousand grains of sand make a heap,
and if removing one grain of sand from a heap leaves a heap,
then one grain of sand is a heap.
The problem is that ‘heap’, like many other common nouns and adjectives (‘red’, for example), is vague. A vague term is one for which something like the second premise of the example holds: along some scale of extensive or intensive quantity applicable to things to which the term applies, if the term applies to x, then it still applies if the quantity of x changes “a little”. Apply that conditional sufficiently many times to an x to which the vague term P applies and you will end up concluding that something we would normally call a clear case of P is in fact not-P.
I conclude, therefore, that what I was looking at was neither a cloud nor reddish-orange. Nor was there a sun shining on it (‘star’ is a vague term too). It’s disappointing, but modus ponens is not to be gainsaid.
Sorites is Greek for ‘heap’. Peter Unger, early in his career, made heavy use of the sorites paradox to show that there are no people, no bodies, and so forth. Michael Dummett noted that most observational predicates of the sort beloved by empiricists (‘red’ as in “red here now” and so forth) are vague: see “Wang’s Paradox” in Truth and other enigmas. For a sample of philosophical work on vagueness, see Vagueness: a reader, ed. Rosanna Keefe and Peter Smith.

LinkMay 11, 2004 in Metaphysics & Epistemology