As already noted (pp. 4.4:6-7), an intellectual good—that is, an idea—need only be produced once, after which it ceases to be scarce and is therefore no longer a good for its producer. No efforts need be expended to increase the "supply" of the idea or to economize its use so that it will not be "spent" too quickly. On the other hand, physical representations of the idea, such as books and databases, may be valuable goods. Ideas realized in such material forms may be highly valuable to other persons in society and are therefore considered worthy of protection in the marketplace, by means to be discussed in Section 5.

Services constitute a special subcategory of goods. We have already seen how Crusoe's labor services function as valuable goods in his structure of production. In a social context, labor services may be purchased from others, either as factors of production or as consumer goods (e. g., medical care). Furthermore, in a fundamental sense all goods are valued for their services to human purposes. Consequently, we need not make a sharp distinction between goods and services.