Source
Wilson and Barker (2007; substantive revision 17 January 2024), “Biological Individuals”, Stanford Encyclopedia of Philosophy, LIT-168, read in NOTE-114.
What was actually shown
Not only organisms (§3.1). Parts of organisms are “often enough, themselves biological individuals”, and so are the populations and lineages organisms form. If compositional complexity is necessary for organisms, “given that there are organisms, there must be some biological individuals that are not organisms”. The stronger form is conditional.
Two kinds (§3.2). Evolutionary against physiological individuality is “the most commonly recognized distinction” (after Pradeu 2016). A Darwinian individual is a member of a population with variation, heritability and differential reproduction, a bearer and active reproducer of heritable traits (Godfrey-Smith 2009). A physiological individual is “a functionally integrated and cohesive metabolic whole, made of interdependent and interconnected parts” (Pradeu 2016b: 807); the entry calls these living agents. Organisms are “exemplars of (but not strictly identical to) both”.
The framework (§§4, 6–7). Biological individuals “include exactly” organisms, some parts and some groups of organisms, which overlap. With the two kinds laid over them, nine regions result, each with an example: fruit fly (organism, living, Darwinian); gene (part, Darwinian only); eusocial insect colony (group, Darwinian only); lysosome (part, neither); a clade such as Bryophyta (group, neither); heart (part, living only); coral reef (group, living only); virus (part, both, by scaffolded reproduction); squid with Vibrio (organism, living only). The authors say some regions “may turn out … unoccupied”.
What could have come out otherwise. The two kinds could have coincided everywhere outside organisms. The placements the entry is least contentious about, genes and hearts, have them coming apart.
What this does not say
- That all nine regions are occupied. Regions 3, 7, 8 and 9 are each hedged (“perhaps”, “more controversially”, “plausible candidate”). The squid and Vibrio placement is offered and at once allowed to disqualify the pair as an organism.
- Which parts and groups count. “Some” is never given a criterion.
- That genes are settled. Bourrat (LIT-157) puts genes in multicellular organisms with hearts, as reproducees, which revisits region 2.
- Anything about parthood. “Part”, “proper part”, “compose” and “member” are used without definition, and the general metaphysics of individuality is “bracketed off” (§1).
- That “living agent” means agent. It is the entry’s term for a physiological individual. In the record’s terms (ADR-024) an individual is not thereby an agent, and the entry’s colonies are agents only “by the cognitive metaphor” (§7).
- That the meta ratio measures individuality. The authors’ extension of Queller and Strassmann (§8) has no operationalization.
- That the text is clean. It places Buchnera in a “human” gut (§4), swaps anabolic and catabolic (§6.1), and misprints Armillaria (§2).
Connections
- QUESTION-035 asks, relative to a stated target, when a combined form is one system. This account constrains the answer for living systems: whether a part or a group is one individual depends on which kind of individuality is the target, evolutionary or physiological, and the two verdicts can differ for the same thing.
- Pregnancy. Meincke (THEORY-448) is a case of the §4 overlap, one organism inside another, argued from the process ontology this entry notes and does not adopt.
- Evolutionary individuality. Clarke’s view (§8), that something is an evolutionary individual if and only if it has mechanisms that inhibit selection among its parts and maintain selection between wholes, is the shape of THEORY-141 on major transitions and of THEORY-135 on suppressing cells that cheat the organism.
- Agency. THEORY-071 makes individuality one condition of minimal agency and not sufficient for it, which is the separation the entry’s “living agent” label blurs.
- Reefs. THEORY-128 and THEORY-130 use the coral reef and holobiont cases this entry leaves open.