As I write, the sky is darkening and the radio warns that a storm is heading towards Boston, expected to bring heavy rain and strong winds, flooding of rivers and coastal areas, damage to trees and homes, and loss of power. The preceding statement, call it S (and pretend it to be spoken), is manifested in an external medium and understood in various ways by speaker and hearers. Informally, we say it has sound and meaning. S is also related to inner states of speaker and hearers, which enter into the ways they interpret it. Communication depends on similarity among these states. In such ways, language engages the world.

These topics have been studied for millennia from many points of view. They are also matters of interest in ordinary life, and there are varying cultural and linguistic practices concerning them, sometimes called “common sense” or “folk science.” Plainly, the study of the topics themselves is not the study of such practices. The earth sciences are not bound by ideas and attitudes expressed in S, and the same holds for Hume's “science of human nature,” which seeks to discover “the secret springs and principles, by which the human mind is actuated in its operations” (1748/1975: 14, Section 9).

While the issues are clear enough for the earth sciences, they are more convoluted when we turn to the science of human nature, which counts among its concerns the investigation of common sense (what we might call ethnoscience).