The criterion for evaluating well-functioning in a tree, a deer, a wolf, or a poison ivy plant, it should be noted, has nothing to do with the organism's possible benefit or harm to human beings. While observations of the latter effects may be significant in determining appropriate human actions, none of these organisms exist to satisfy human needs. In order fully to understand the nature and existence of a poison ivy plant, we must momentarily renounce an anthropocentric viewpoint, acknowledging that the plant needs to produce a toxic substance in order to protect itself against other organisms that might otherwise be harmful to it. Production of that toxin is thus part of the proper function of a healthy poison ivy plant. Only in those cases where humans have played a role in the evolution of a species or breed (e. g., dogs; see p. 1.4:24) may human needs become relevant to well-functioning in that organism.

The concept of well-functioning cannot be meaningfully applied to inanimate, non-life-made objects. For example, an asteroid cannot "function well" or "function poorly," since its existence cannot be attributed to any needs of living beings. The concept thus applies only to those entities that were identified in Section 1 as functional (pp. 1.4:22-9). In summary, a functional entity is well-functioning insofar as it effectively serves the need(s) that explain its existence.