Concepts of "function" and function-based entities—including organisms, components of organisms (such as organs), and life-made entities (such as tools)—will be developed at length in the subsection on "Metaphysics." Because function-based entities are often adapted to environmental factors that must adhere to particular ranges of values, differences of degree may be associated with differences in kind. In this instance, leg length below a certain threshold adversely affects a smiley's access to fruit (i. e., its nutritional function), thereby generating a difference in kind.

For another illustration, consider the concept "table," which Rand defines as "a man-made object consisting of a flat, level surface and support(s), intended to support other, smaller objects" (Introduction to Objectivist Epistemology, p. 14; more information). Because a 20-foot-tall or 0.2-inch-tall structure would probably be impractical for the utilitarian purpose specified in this definition, we would regard such extreme structures as different in kind—and not just in measurements—from ordinary tables.