"Vitalism" is primarily a metaphysical doctrine concerning the nature of living organisms, although it has been generalized, by Henri Bergson for example, into a comprehensive metaphysics applicable to all phenomena. We shall examine vitalism only as a theory of life.

There have been three general answers to the question "What distinguishes living from nonliving things?" The first, and currently most fashionable, answer is "A complex pattern of organization in which each element of the pattern is itself a nonliving entity." In this view, a living organism, and each of its living parts, is exhaustively composed of inanimate parts; and these parts have no relations except those that are also exhibited in inanimate systems. The second answer is "The presence in living systems of emergent properties, contingent upon the organization of inanimate parts but not reducible to them." This answer resembles the first in acknowledging that a living system...