In accordance with Leopold's oft-quoted dictum — "A thing is right when it tends to preserve the integrity, stability, and beauty of the biotic community. It is wrong when it tends otherwise" — Callicott espouses a holistic, non-anthropocentric environmental ethic. What he labels the “extentionist” approach to environmental ethics attempts to extend familiar anthropocentric ethical paradigms — legacies of the European Enlightenment — to other-than-human beings. Peter Singer’s “animal liberation,” for example, extends Jeremy Bentham’s utilitarian ethical paradigm to all sentient animals. Paul W. Taylor's “biocentrism” extends the Kantian deontological paradigm to all “teleological centers of life” (i.e. all organisms). Extensionist approaches, however, are inveterately individualistic, conferring “moral considerability” on individual organisms. Actual environmental concerns, however, focus on transorganismic entities: endangered species; threatened biotic communities and ecosystems; rivers and lakes; the ocean and atmosphere. Callicott believes that an adequate environmental ethic — an environmental-ethics paradigm that addresses actual environmental concerns — must be holistic.