organism a carbon-based living thing or substance, e.g., a paramecium, a tree, or an ant. Alternatively, ‘organism’ can mean a hypothetical living thing of another natural kind, e.g., a silicon-based living thing. Defining conditions of a carbon-based living thing, x, are as follows. (1) x has a layer made of m-molecules, i.e., carbonbased macromolecules of repeated units that have a high capacity for selective reactions with other similar molecules. x can absorb and excrete through this layer. (2) x can metabolize m-molecules. (3) x can synthesize m-molecular parts of x by means of activities of a proper part of x that is a nuclear molecule, i.e., an m-molecule that can copy itself. (4) x can exercise the foregoing capacities in such a way that the corresponding activities are causally interrelated as follows: x’s absorption and excretion causally contribute to x’s metabolism; these processes jointly causally contribute to x’s synthesizing; and x’s synthesizing causally contributes to x’s absorption, excretion, and metabolism. (5) x belongs to a natural kind of compound physical substance that can have a member, y, such that: y has a proper part, z; z is a nuclear molecule; and y reproduces by means of z’s copying itself. (6) x is not possibly a proper part of something that satisfies (1)–(6). The last condition expresses the independence and autonomy of an organism. For example, a part of an organism, e.g., a heart cell, is not an organism. It also follows that a colony of organisms, e.g., a colony of ants, is not an organism. See also LIFE, ORGANIC , ORGANICIS.
J.Ho. & G.Ro.