Abstract
The ‘species problem’ is that there are multiple ways to conceive species that divide up biodiversity in inconsistent ways. Monistic responses to the species problem seek a single universal species concept, no single concept seems adequate though. Pluralistic responses recognise multiple species concepts, based on differences across biodiversity, theoretical interests or the functioning of concepts. But if what counts as a species taxon depends on human interests it isn't clear that species concepts divide biodiversity into real units and ‘cut nature at its joints’ in a straightforward way. The reality of species also seems to depend on their metaphysical status: what basic kinds of things are they? Some argue that species are sets of organisms, based on real essences, clusters of properties or historical relations. Others argue that they are spatiotemporally restricted individuals analogous to organisms.
Key Concepts:
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The species problem is the use of multiple inconsistent species concepts that divide biodiversity in different ways.
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Monism is the view that correctly understood, there is only one kind of species thing.
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Natural kinds are groupings that are independent of human conventions and preferences, and are studied by science.
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Pluralism is the view that there are two or more kinds of species things.
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Pragmatic pluralism is the view that organisms can be grouped into species on the basis of different research interests.
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Realism is the view that species taxa are real and independent of human conventions.
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The species‐as‐individuals thesis is that species are historical individuals with beginnings, endings, change over time and cohesion. Organisms are ‘parts’ of a species.
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The species‐as‐sets thesis is that species are sets of organisms, where set inclusion is determined by intrinsic or extrinsic properties. Organisms are ‘members’ of a species.
Keywords: essentialism; natural kinds; cluster kinds; species problem; species concepts; species pluralism; species as sets, species as individuals