This paper is a critical discussion of John Dupré's recent defence of promiscuous realism in Part 1 of his The Disorder of Things: Metaphysical Foundations of the Disunity of Science. It also discusses some more general issues in the philosophy of biology and science. Dupré's chief strategy of argumentation appeals to debates within the philosophy of biology, all of which concern the nature of species. While the strategy is well motivated, I argue that Dupré's challenge to essentialist and unificationist views (...) about natural kinds is not successful. One conclusion is that an integrative conception of species is a real alternative to Dupré's pluralism. (shrink)

This paper outlines an alternative perspective on species that avoids some of the underlying assumptions held by the BSC and other gene-centred species concepts. It begins with a characterisation of the species problem and some of the assumptions underpinning conceptions of species. In particular, the underlying bias of some conceptions (such as the BSC) to focus exclusively on the adult stage of the life cycle in articulating what a species is.

Standard biological and philosophical treatments assume that dramatic genotypic or phenotypic change constitutes instantaneous speciation, and that barring such saltation, speciation is gradual evolutionary change in individual properties. Both propositions appear to be incongruent with standard theoretical perspectives on species themselves, since these perspectives are (a) non-pheneticist, and (b) tend to disregard intermediate cases. After reviewing certain key elements of such perspectives, it is proposed that species-membership is mediated by membership in a population. Species-membership depends, therefore, not on intrinsic characteristics (...) of an organism, but on relationship of an organism to others. A new definition of speciation is proposed in the spirit of this proposal. This definition implies that dramatic change is neither necessary nor sufficient for speciation. It also implies, surprisingly, that an organism can change species during its lifetime. (shrink)

While Darwin is commonly supposed to have demonstrated the inapplicability of the Aristotelian ontology of species to biological science, recent developments, especially in the wake of the Human Genome Project, have given rise to a new golden age of classification in which ontological ideas -- as for example in the Gene Ontology, the Cell Ontology, the Protein Ontology, and so forth -- are once again playing an important role. In regard to species, on the other hand, matters are more complex. (...) We provide a brief overview of recent proposals concerning the ontology of species, dealing with species as sets, classes and as collections, the views of Ernst Meyr, and mereological views. (shrink)

The article defends the doctrine that Linnaean taxa, including species, have essences that are, at least partly, underlying intrinsic, mostly genetic, properties. The consensus among philosophers of biology is that such essentialism is deeply wrong, indeed incompatible with Darwinism. I argue that biological generalizations about the morphology, physiology, and behavior of species require structural explanations that must advert to these essential properties. The objection that, according to current “species concepts,” species are relational is rejected. These concepts are primarily concerned with (...) what it is for a kind to be a species and throw little light on the essentialist issue of what it is for an organism to be a member of a particular kind. Finally, the article argues that this essentialism can accommodate features of Darwinism associated with variation and change. (shrink)

This paper analyzes the concept of biodiversity in conservation biology and assesses potential methods for its measurement.

This paper surveys recent philosophy of biology. It aims to introduce outsiders to the field to the recent literature (which is reviewed in the footnotes) and the main recent debates. I concentrate on three of these: recent critiques of the replicator/vehicle distinction and its application to the idea of the gene as the unit of section; the recent defences of group selection and the idea that standard alternatives to group selection are in fact no more than a disguised form of (...) group selection; and recent ideas on the role of selection in evolution, especially the role of selection in structuring the large-scale history of life. The paper connects philosophy of biology to some more general problems in the philosophy of science, and concludes with a few suggestions about unfinished business. (shrink)

I have recently argued that origin essentialism regarding individual organisms entails that natural selection does not explain why individual organisms have the traits that they do. This paper defends this and related theses against Mohan Matthen's recent objections.

Philosophical discussions of species have focused on multicellular, sexual animals and have often neglected to consider unicellular organisms like bacteria. This article begins to fill this gap by considering what species concepts, if any, apply neatly to the bacterial world. First, I argue that the biological species concept cannot be applied to bacteria because of the variable rates of genetic transfer between populations, depending in part on which gene type is prioritized. Second, I present a critique of phylogenetic bacterial species, (...) arguing that phylogenetic bacterial classification requires a questionable metaphysical commitment to the existence of essential genes. I conclude by considering how microbiologists have dealt with these biological complexities by using more pragmatic and not exclusively evolutionary accounts of species. I argue that this pragmatism is not borne of laziness but rather of the substantial conceptual problems in classifying bacteria based on any evolutionary standard. (shrink)

This paper takes up the cause of species pluralism. An argument for species pluralism is provided and standard monist objections to pluralism are answered. A new form of species pluralism is developed and shown to be an improvement over previous forms. This paper also offers a general foundation on which to base a pluralistic approach to biological classification.

Species pluralism gives us reason to doubt the existence of the species category. The problem is not that species concepts are chosen according to our interests or that pluralism and the desire for hierarchical classifications are incompatible. The problem is that the various taxa we call 'species' lack a common unifying feature.

This paper explains the metaphysical implications of the view that species are individuals (SAI). I first clarify SAI in light of the separate distinctions between individuals and classes, particulars and universals, and abstract and concrete things. I then show why the standard arguments given in defense of SAI are not compelling. Nonetheless, the ontological status of species is linked to the traditional "species problem," in that certain species concepts do entail that species are individuals. I develop the idea that species (...) names are rigid designators and show how this provides additional motivation for SAI. (shrink)

Editors' introduction to the special issue on homology (Biology and Philosophy Vol. 22, Issue 5, 2007).

This paper offers an overview of "the species problem", arguing for a view of species as homeostatic property cluster kinds, positioning the resulting form of realism about species as an alternative to the claim that species are individuals and pluralistic views of species. It draws on taxonomic practice in the neurosciences, especially of neural crest cells and retinal ganglion cells, to motivate both the rejection of the species-as-individuals thesis and species pluralism.

In this paper we recall, improve, and extend several definitions, properties and applications of our previous 2019 research referred to NeutroAlgebras and AntiAlgebras (also called NeutroAlgebraic Structures and respectively AntiAlgebraic Structures). Let <A> be an item (concept, attribute, idea, proposition, theory, etc.). Through the process of neutrosphication, we split the nonempty space we work on into three regions {two opposite ones corresponding to <A> and <antiA>, and one corresponding to neutral (indeterminate) <neutA> (also denoted <neutroA>) between the opposites}, which may (...) or may not be disjoint – depending on the application, but they are exhaustive (their union equals the whole space). A NeutroAlgebra is an algebra which has at least one NeutroOperation or one NeutroAxiom (axiom that is true for some elements, indeterminate for other elements, and false for the other elements). A Partial Algebra is an algebra that has at least one Partial Operation, and all its Axioms are classical (i.e. axioms true for all elements). Through a theorem we prove that NeutroAlgebra is a generalization of Partial Algebra, and we give examples of NeutroAlgebras that are not Partial Algebras. We also introduce the NeutroFunction (and NeutroOperation). (shrink)

The impressive variation amongst biological individuals generates many complexities in addressing the simple-sounding question what is a biological individual? A distinction between evolutionary and physiological individuals is useful in thinking about biological individuals, as is attention to the kinds of groups, such as superorganisms and species, that have sometimes been thought of as biological individuals. More fully understanding the conceptual space that biological individuals occupy also involves considering a range of other concepts, such as life, reproduction, and agency. There has (...) been a focus in some recent discussions by both philosophers and biologists on how evolutionary individuals are created and regulated, as well as continuing work on the evolution of individuality. (shrink)

This Ph.D. thesis provides a pilosophical account of the structure of the evolutionary synthesis of the 1930s and 40s. The first, more historical part analyses how classical genetics came to be integrated into evolutionary thinking, highlighting in particular the importance of chromosomal mapping of Drosophila strains collected in the wild by Dobzansky, but also the work of Goldschmidt, Sumners, Timofeeff-Ressovsky and others. The second, more philosophical part attempts to answer the question wherein the unity of the synthesis consisted. I argue (...) that it exemplifies a weak of form of explanatory unification. (shrink)

Discussions of the functions of biological traits generally take the notion of a trait for granted. Defining this notion is a non-trivial problem. Different approaches to function place different constraints on adequate accounts of the notion of a trait. Accounts of function based on engineering-style analyses allow trait boundaries to be a matter of human interest. Accounts of function based on natural selection have typically been taken to require trait boundaries that are objectively real. After canvassing problems raised by each (...) approach, I conclude with some facts that satisfactory notions of trait must respect. (shrink)

Species concepts aim to define the species category. Many of these rely on defining species in terms of natural lineages and groupings. A dominant gene-centred metaconception has shaped notions of what constitutes both a natural lineage and a natural grouping. I suggest that relying on this metaconception provides an incomplete understanding of what constitute natural lineages and groupings. If we take seriously the role of epigenetic, behavioural, cultural, and ecological inheritance systems, rather than exclusively genetic inheritance, a broader notion of (...) what constitutes a natural grouping or lineage may be required. I conclude by outlining an alternative metaconception that is a de-centred metaschema for species. (shrink)

The project of this paper is to understand what a phylogenetic tree represents and to discuss some of the implications that this has for the practice of systematics. At least the first part of this task, if not both parts, might appear trivial—or perhaps better suited for a single page in a textbook rather than a scholarly research paper. But this would be a mistake. While the task of interpreting phylogenetic trees is often treated in a trivial way, their interpretation (...) is tied to foundational conceptual questions at the heart of systematics—questions whose answers are hotly disputed. I have previously argued that widely shared ideas about the meaning and interpretation of phylogenetic trees are inconsistent with species concepts other than some genealogical version of a phylogenetic species concept (Velasco 2008). Here I rely on a similar approach and concentrate on the implications of the necessary conditions underlying the inferences that we make using phylogenetic trees. I argue that common practices for the interpretation and use of trees are in conflict and that unacceptable principles about species as units of phylogeny must be given up. According to the view that I will develop, all phylogenetic trees depict the history of populations. The branches on trees represent collections of population lineages through time and the splits represent population lineage splits. This is true regardless of whether the tips of the trees are themselves populations, or are species or higher taxa. Although this conclusion might be paired naturally with a view that species must be monophyletic groups, this population-centric view of trees is independent of that view of species. If we still want to have species that are paraphyletic groups of populations, this is permissible as long as we also do not treat species as the units of phylogeny. This population-centric view opposes a species-centric view of phylogeny and might be called a “rank-free” approach since it entails that we do not need to determine which groups are species (which is partly a ranking question) in order to build a tree. This conclusion and the argument for it are meant to be consistent with, but not require, acceptance of the conclusions of Velasco (2008) regarding species. (shrink)

Darwinism designates a distinctive form of evolutionary explanation for the history and diversity of life on earth. Its original formulation is provided in the first edition of On the Origin of Species in 1859. This entry first formulates ‘Darwin's Darwinism’ in terms of five philosophically distinctive themes: (i) probability and chance, (ii) the nature, power and scope of selection, (iii) adaptation and teleology, (iv) nominalism vs. essentialism about species and (v) the tempo and mode of evolutionary change. Both Darwin and (...) his critics recognized that his approach to evolution was distinctive on each of these topics, and it remains true that, though Darwinism has developed in many ways unforeseen by Darwin, its proponents and critics continue to differentiate it from other approaches in evolutionary biology by focusing on these themes. This point is illustrated in the second half of the entry by looking at current debates in the philosophy of evolutionary biology on these five themes, with a special focus on Stephen Jay Gould's The Structure of Evolutionary Theory. (shrink)

Gayon's recent claim that Buffon developed a concept of species as physical individuals is critically examined and rejected. Also critically examined and rejected is Gayon's more central thesis that as a consequence of his analysis of Buffon's species concept, and also of Darwin's species concept, it is clear that modern evolutionary theory does not require species to be physical individuals. While I agree with Gayon's conclusion that modern evolutionary theory does not require species to be physical individuals, I disagree with (...) his reasons and instead provide logical rather than historical reasons for the same conclusion. (shrink)

This paper critically examines the biology of species identity and the morality of crossing species boundaries in the context of emerging research that involves combining human and nonhuman animals at the genetic or cellular level. We begin with the notion of species identity, particularly focusing on the ostensible fixity of species boundaries, and we explore the general biological and philosophical problem of defining species. Against this backdrop, we survey and criticize earlier attempts to forbid crossing species boundaries in the creation (...) of novel beings. We do not attempt to establish the immorality of crossing species boundaries, but we conclude with some thoughts about such crossings, alluding to the notion of moral confusion regarding social and ethical obligations to novel interspecies beings. (shrink)

In this paper I take issue with the doctrine that organisms belong of their very essence to the natural kinds (or biological taxa, if these are not kinds) to which they belong. This view holds that any human essentially belongs to the species Homo sapiens, any feline essentially belongs to the cat family, and so on. I survey the various competing views in biological systematics. These offer different explanations for what it is that makes a member of one species, family, (...) etc. a member of that taxon. Unfortunately, none of them offers an explanation that is compatible with the essentialism in question. (shrink)

Kinds that share historical properties are dubbed “historical kinds” or “etiological kinds,” and they have some distinctive features. I will try to characterize etiological kinds in general terms and briefly survey some previous philosophical discussions of these kinds. Then I will take a closer look at a few case studies involving different types of etiological kinds. Finally, I will try to understand the rationale for classifying on the basis of etiology, putting forward reasons for classifying phenomena on the basis of (...) diachronic features, thereby making a provisional case for considering at least some etiological kinds to be natural kinds. (shrink)

The concept of species is one of the core concepts in biology and one of the cornerstones of evolutionary biology, yet it is rife with conceptual problems. Philosophers of biology have been discussing the concept of species for decades, and in doing so they sometimes appeal to the views of biologists. However, their statements as to what biologists think are seldom supported by empirical data. In order to investigate what biologists actually think about the key issues related to the problem (...) of species, we have conducted a survey on the sample of 193 biologists from the population of biologists from over 150 biology departments at universities in the US and the EU. This article presents and discusses the results of the survey. Some results confirm and others falsify the reiterated statements of philosophers of biology as to what biologists think, but all results we obtained should be informative and relevant for future discussions of the problem of species. (shrink)

A few philosophers of biology have recently explicitly rejected Essential Membership, the doctrine that if an individual organism belongs to a taxon, particularly a species, it does so essentially. But philosophers of biology have not addressed the broader issue, much discussed by metaphysicians on the basis of modal intuitions, of what is essential to the organism. In this paper, I address that issue from a biological basis, arguing for the Kripkean view that an organism has a partly intrinsic, partly historical, (...) essence. The arguments appeal to the demands of biological explanation and are analogous to arguments that I have given elsewhere that a taxon has a partly intrinsic, partly historical, essence. These conclusions about the essences of individuals and taxa yield an argument for Essential Membership. Finally, I cast doubt on LaPorte’s objection to that doctrine arising from the view that a species cannot survive having a daughter. (shrink)

To date, no definition of life has been unequivocally accepted by the scientific community. In frustration, some authors advocate alternatives to standard definitions. These include using a list of characteristic features, focusing on life’s effects, or categorizing biospheres rather than life itself; treating life as a fuzzy category, a process or a cluster of contingent properties; or advocating a ‘wait-and-see’ approach until other examples of life are created or discovered. But these skeptical, operational, and pluralistic approaches have intensified the debate, (...) rather than settled it. Given the failure of even these approaches, we advocate a new strategy. In this paper, we reverse the usual line of reasoning and argue that the “life problem” arises from thinking incorrectly about the nature of life. Scientists most often conceptualize life as a class or kind, with earthly life as a single instance of it. Instead, we advocate thinking about Earth’s Life as an individual, in the way that species are now thought to be. In this view, Life is a monophyletic clade that originated with a last universal common ancestor, and includes all its descendants. We can continue to use the category ‘life’ pragmatically to refer to similarities between various phenomena and Life. But the relevant similarities are a matter of interest and preference, not a matter of fact. The search for other life in the Universe, then, is merely a search for entities that resemble parts of Life in whatever sense astrobiologists find most appealing. This does not mean that the search for evolved complexity elsewhere in the universe or its creation in the lab are futile endeavors, but that debates over whether they count as ‘life’ are. Ironically, finally abandoning the concept ‘life’ may make our searches for evolved complexity more fruitful. We explain why. (shrink)

Pluralist and eliminativist positions have proliferated within both science and philosophy of science in recent decades. This paper asks the question why this shift of thinking has occurred, and where it is leading us. We provide an explanation which, if correct, entails that we should expect pluralism and eliminativism to transform other debates currently unaffected, and for good reasons. We then consider the question under what circumstances eliminativism will be appropriate, arguing that it depends not only on the term in (...) question, but also on the context of discussion and details of the debate at hand. The resultant selective eliminativism is an appealing compromise for various ‘pluralists’ and ‘eliminativists’ who are currently locking horns. (shrink)

Exploring whether clades can reproduce leads to new perspectives on general accounts of biological development and individuation. Here we apply James Griesemer's general account of reproduction to clades. Griesemer's account of reproduction includes a requirement for development, raising the question of whether clades may bemeaningfully said to develop. We offer two illustrative examples of what clade development might look like, though evaluating these examples proves difficult due to the paucity of general accounts of development. This difficulty, however, is instructive about (...) what a general account of development should look like and how it may usefully be applied to research problems (further suggesting a means for evaluating general accounts of development). Reproduction also requires individuation of parent and offspring. We argue that there is no special problem of individuating older and younger clades. The vagaries involved with determining when clades begin, mature, and end are precisely the same as those that arise when the same questions are asked of cells, organisms, or species. Though the question of clade reproduction and selection may still be open, the process of discovery presents new insights into old problems. (shrink)

In addition to the distinction between species as a category and speciesas a taxon, the word species is ambiguous in a very different butequally important way, namely the temporal distinction between horizontal andvertical species. Although often found in the relevant literature, thisdistinction has thus far remained vague and undefined. In this paper the use ofthe distinction is explored, an attempt is made to clarify and define it, andthen the relation between the two dimensions and the implications of thatrelation are examined. (...) Using Darwin's analogy of language evolution forspeciesevolution, and by appealing to a major change in the conception of languagebetween 19th- and 20th-century linguistics, it is argued that the horizontaldimension has priority (pragmatic, epistemological, logical, and ontological)over the vertical dimension. This has immense ramifications for the modernspecies problem. Fundamentally, it favors horizontal species concepts oververtical ones. In so doing it places species realism on a much more securefoundation and largely undercuts species pluralism. In addition it raises aserious problem for the increasingly popular family of phylogenetic speciesconcepts, which generally suffer from a dimensionality confusion. However,thereis a recent trend within this family that attempts to restore the priority ofthe horizontal dimension. It is concluded that this trend should be affirmedandthat the species-as-individuals view should be abandoned. (shrink)

The variation and selection form of explanationcan be prescinded from the evolutionary biologyhome ground in which it was discovered and forwhich it has been most developed. When this isdone, variation and selection explanations arefound to have potential application to a widerange of phenomena, far beyond the classicalbiological ground and the contemporaryextensions into epistemological domains. Itappears as the form of explanation most suitedto phenomena of fit. It is also found toparticipate in multiple interestingrelationships with other forms of explanation. We proceed with (...) an examination of multiplekinds of phenomena, interrelationships withother members of the family of forms ofexplanation, and some novel applications evenwithin the home ground of evolutionary biology. (shrink)

Metaphysical investigation often proceeds by way of linguistic meaning. This tradition relies on an assumption about meanings, namely that they can be given in terms of referential relations and truth. Chomsky and others have illustrated the difficulty with this externalist hypothesis regarding natural language meanings, which implies that natural languages are ill‐suited for the purposes of metaphysical investigation. In reply to this discordance between the features of natural languages and the goals of metaphysical investigation, metaphysicians propose that we look to (...) the invented languages used to express our best scientific theories as metaphysical guides, in the hope that these languages are better behaved. I argue that this retreat is beset with similar troubles for the metaphysician. In particular, I argue that central terms in the field of biology, namely ‘gene’ and ‘species’, exhibit a kind of lexical flexibility that renders them, much like their natural language counterparts, ill‐suited for the metaphysician's aims. (shrink)

Recent work has suggested that conservation efforts such as restoration ecology and invasive species eradication are largely value-driven pursuits. Concurrently, changes to global climate are forcing ecologists to consider if and how collections of species will migrate, and whether or not we should be assisting such movements. Herein, we propose a philosophical framework which addresses these issues by utilizing ecological and evolutionary interrelationships to delineate individual ecological communities. Specifically, our Evolutionary Community Concept recognizes unique collections of species that interact and (...) have co-evolved in a given geographic area. We argue this concept has implications for a number of contemporary global conservation issues. Specifically, our framework allows us to establish a biological and science-driven context for making decisions regarding the restoration of systems and the removal of exotic species. The ECC also has implications for how we view shifts in species assemblages due to climate change and it advances our understanding of various ecological concepts, such as resilience. (shrink)

Building upon a non-standard understanding of evolutionary process focusing on variation and persistence, I will argue that communities and ecosystems can evolve by natural selection as emergent individuals. Evolutionary biology has relied ever increasingly on the modeling of population dynamics. Most have taken for granted that we all agree on what is a population. Recent work has reexamined this perceived consensus. I will argue that there are good reasons to restrict the term “population” to collections of monophyletically related replicators and (...) interactors, which explains why many existing models in population biology exclude by definition many genuine evolving biological individuals such as communities and ecosystems. By studying a case of community evolution (a symbiotic termite–fungus community), we will see that it is variation that is important to evolutionary processes, not populations. Variation within a population is only one of many types of variation that can lead to evolution by natural selection. The upshot of focusing on variation is that cases of community and ecosystem adaptive change become tractable in evolutionary terms. I will show that complex emergent individuals such as communities and ecosystems cannot be fully accommodated by conventional population/reproduction models but can be accommodated by variation/persistence models. (shrink)

Integration (interaction among parts of an entity) is suggested to be necessary for individuality (contra, Metaphysics and the Origin of Species). A synchronic species is an integrated individual that can evolve as a unified whole; a diachronic lineage is a non-integrated historical entity that cannot evolve. Synchronic species and diachronic lineages are consequently suggested to be ontologically distinct entities, rather than alternative perspectives of the same underlying entity (contra Baum (1998), Syst. Biol. 47, 641–653; de Queiroz (1995), Endless Forms: Species (...) and Speciation, pp. 57–75; Genes, Categories and Species). Species concepts usually refer to either one or the other entity; for instance, the Biological Species Concept refers to synchronic species, whereas the Cladistic Species Concept refers to diachronic lineages. The debate over species concepts has often failed to recognise this distinction, resulting in invalid comparisons between definitions that attempt to delineate fundamentally different entities. (shrink)

This paper argues that typical biological species are natural kinds, on a familiar realist understanding of natural kinds—classes of individuals across which certain properties cluster together, in virtue of the causal workings of the world. But the clustering is far from exceptionless. Virtually no properties, or property-combinations, characterize every last member of a typical species—unless they can also appear outside the species. This motivates some to hold that what ties together the members of a species is the ability to interbreed, (...) others that it is common descent. Yet others hold that species are scattered individuals,of which organisms are parts rather than members. But not one of these views absolves us of the need to posit a typical phenotypic profile. Vagueness is here to stay. Some seek to explain the vagueness by saying species are united by “homeostatic property clusters”; but this view collapses into the more familiar realist picture. (shrink)

This paper examines the species problem in microbiology and its implications for the species problem more generally. Given the different meanings of ‘species’ in microbiology, the use of ‘species’ in biology is more multifarious and problematic than commonly recognized. So much so, that recent work in microbial systematics casts doubt on the existence of a prokaryote species category in nature. It also casts doubt on the existence of a general species category for all of life (one that includes both prokaryotes (...) and eukaryotes). Prokaryote biology also undermines recent attempts to save the species category, such as the suggestion that species are metapopulation lineages and the idea that ‘species’ is a family resemblance concept. (shrink)

Most biologists use the Linnaean system for constructing classifications of the organic world. The Linnaean system, however, has lost its theoretical basis due to the shift in biology from creationist and essentialist tenets to evolutionary theory. As a result, the Linnaean system is both cumbersome and ontologically vacuous. This paper illustrates the problems facing the Linnaean system, and ends with a brief introduction to an alternative approach to biological classification.

There is no question that the constituents of cells and organisms are joined together by the part-whole relation. Genes are part of cells, and cells are part of organisms. Species taxa, however, have traditionally been conceived of, not as wholes with parts, but as classes with members. But why does the relation change abruptly from part-whole to class-membership above the level of organisms? Ghiselin, Hull and others have argued that it doesn't. Cells and organisms are cohesive mereological sums, and since (...) species taxa are like cells and organisms in the relevant respects, they, too, are cohesive mereological sums. I provide further reasons in support of the thesis that species are mereological sums. I argue, moreover, that the advocate of this thesis is committed to a form of pluralism with respect to the species concept. (shrink)

Talk of higher categories (ranks) like Genus and Family is ubiquitous in biology. Yet there is widespread skepticism about these categories. We can locate the source of this skepticism in the lack of “robust concepts” for these categories, robust theories of what it is to be in a certain category. A common defense of category talk is that its virtues are “just pragmatic and not theoretic”. But this strains credulity. We should suppose rather that talk of the higher categories does (...) theoretical work. What work? The paper proposes a “minimal concept” for a category, according to which the category is at least explanatory in marking out, in a rough and ready way, a level in the hierarchy of explanatory taxa. The skepticism is exaggerated. (shrink)

The circumscription of taxa and classification of organisms are fundamental tasks in the systematization of biological diversity. Their success depends on a unified idea concerning the species concept, evolution, and taxonomy; paradoxically, however, it requires a complete distinction between taxa and evolutionary units. To justify this view, I discuss these three topics of systematics. Species concepts are examined, and I propose a redefinition for the Taxonomic Species Concept based on nomenclatural properties, in which species are classes conventionally represented by a (...) binomial. Speciation is subsequently discussed, to demonstrate that concepts on the evolutionary process are damaged when species are considered as evolutionary units. Speciation should be considered a transition among patterns of a population and, consequently, always a sympatric process. This view contrasts with the majority of speciation models, which analyze cladogeneses and classify speciation geographically, usually considering allopatry the essential condition for the differentiation process. Finally, taxonomy is considered, to show that the equivalence between evolutionary and taxonomic units may also damage the practice of biological systematization. Principles and rules of nomenclature and classification should offer freedom to accommodate divergent opinions about systematics and to incorporate the evolution of knowledge; therefore, they should remain independent of biological theories. (shrink)