Morphological elements, or structures, are sorted into four categories depending on their level of anatomical isolation and the presence or absence of intrinsically identifying characteristics. These four categories are used to highlight the difficulties with the concept of structure and our ability to identify or define structures. The analysis is extended to the concept of homology through a discussion of the methodological and philosophical problems of the current concept of homology. It is argued that homology is fundamentally a similarity based (...) concept rather than a phylogenetic concept, and a proposal is put forth to return to a comparative context for homology. It is shown that for both the concepts of structure and homology ana priori assumption of stable underlying patterns (i.e. archetypes) is essential. (shrink)

The biological species (biospecies) concept applies only to sexually reproducing species, which means that until sexual reproduction evolved, there were no biospecies. On the universal tree of life, biospecies concepts therefore apply only to a relatively small number of clades, notably plants andanimals. I argue that it is useful to treat the various ways of being a species (species modes) as traits of clades. By extension from biospecies to the other concepts intended to capture the natural realities of what keeps (...) taxa distinct, we can treat other modes as traits also, and so come to understand that theplurality of species concepts reflects the biological realities of monophyletic groups.We should expect that specialists in different organisms will tend to favour those concepts that best represent the intrinsic mechanisms that keep taxa distinct in their clades. I will address the question whether modes ofreproduction such as asexual and sexual reproduction are natural classes, given that they are paraphyletic in most clades. (shrink)

What are species? One popular answer is that species are individuals. Here I develop another approach to thinking about species, an approach based on the notion of a lineage. A lineage is a sequence of reproducing entities, individuated in terms of its components. I argue that one can conceive of species as groups of lineages, either organism lineages or population lineages. Conceiving of species as groups of lineages resolves the problems that the individual conception of species is supposed to resolve. (...) It has added the virtue of focusing attention on the characteristic of species that is most relevant to understanding their role in evolutionary processes, namely, the lineage structure of species. (shrink)

Concepts and methods originating in one discipline can distort the structure of another when they are applied to the latter. I exemplify this mostly with reference to systematic biology, especially problems which have arisen in relation to the nature of species. Thus the received views of classes, individuals (which term I suggest be replaced by units to avoid misunderstandings), and sets are all inapplicable, but each can be suitably modified. The concept of fuzzy set was developed to deal with species (...) and I defend its applicability. Taxa at all levels are real and participate in biological processes. Analysis of cause and pattern provides the deep structure in which metabiology is grounded; violation of this principle has led to diverse errors in biology. (shrink)

This paper uses two case studies to explore an interest-relative view of taxonomy and how it complements kind pluralism in biology. First, I consider the ABC island bear, which can be correctly classified into more than one species. I argue that this classificatory pluralism can be explained by reference to the range of alternative explanatory interests in biology. In the second half of the paper, I pursue an interest-relative view of classification more generally. I then apply the resultant view to (...) a second case study: whether whales are fish. I argue that this question is not one about scientific vs folk usage, as has been assumed. I also develop a new view: that Fish should be rejected as a category, both from the point of view of biological science, and from the point of view of folk taxonomy. Along the way, I use the interest-relative view to shed light on the circumstances under which higher taxa should be accepted as legitimate categories for biological science. (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)

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)

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)

Some astronomers believe that we have discovered that Pluto is not a planet. I contest this assessment. Recent discoveries of trans-Neptunian Pluto-sized objects do not require that we exclude Pluto from the planets. But the obvious alternative, that classificatory revision is a matter of arbitrary choice, is also unpalatable. I argue that this classificatory controversy — which I compare to the controversy about the classification of the platypus — illustrates how our classificatory practices are laden with normative commitments of a (...) distinctive kind. I argue that the “norm-ladenness” of classification has philosophically significant ramifications for how we think about scientific disputes and debates in the metaphysics of classification such as the monism/pluralism debate. (shrink)

A number of influential biologists are currently pursuing efforts to restore previously extinct species. But for decades, philosophers of biology have regarded “de-extinction” as conceptually incoherent. Once a species is gone, it is gone forever. We argue that a range of metaphysical, biological, and ethical grounds for opposing de-extinction are at best inconclusive and that a pragmatic stance that allows for its possibility is more appealing.

In this paper, we discuss the following four alternative ways of understanding the outcomes of resurrection biology. Implications of each of the ways are discussed with respect to concepts of species and extinction. Replication: animals created by resurrection biology do not belong to the original species but are copies of it. The view is compatible with finality of extinction as well as with certain biological and ecological species concepts. Re-creation: animals created are members of the original species but, despite their (...) existence, the species remains extinct. The view is incompatible with all species concepts presented. Non-extinction: animals produced belong to the original species which actually never went extinct. The view may be consistent with phenetic and phylogenetic species concepts as well as with finality of extinction. According to literal resurrection, resurrection biology is successful in reversing extinction through the creation of new members of species that once went extinct. This view presupposes non-finality of extinction and it is compatible with phenetic species concepts. It is notable that no species or extinction concept is consistent with all possible views of resurrection biology nor is any view of resurrection biology consistent with all species or extinction concepts. Thus, one’s views regarding species and extinction determine which views one can adopt regarding resurrection biology and vice versa. (shrink)

Because of the problems associated with ecological concepts, generalizations, and proposed general theories, applied ecology may require a new "logic" of explanation characterized neither by the traditional accounts of confirmation nor by the logic of discovery. Building on the works of Grunbaum, Kuhn, and Wittgenstein, we use detailed descriptions from research on conserving the Northern Spotted Owl, a case typical of problem solving in applied ecology, to (1) characterize the method of case studies; (2) survey its strengths; (3) summarize and (...) respond to its shortcomings; and (4) investigate and defend its underlying "logic". (shrink)

Some philosophers of biology state that the metaphysical status of biological species is context determined by the use different branches of biology make of their corresponding proper names, so that one and the same biological species can be both an individual and a natural kind. In this paper, I aim to undermine the idea, often associated with the present thesis, according to which the debate about the metaphysical status of biological species should be deflated, since it would be possible to (...) translate every sentence from natural-kind talk to individual-talk and vice versa. I offer a charitable interpretation of the principle grounding such an idea and show how it is in tension with independent theoretical biological notions. (shrink)

The correct explanation of why species, in evolutionary theory, are individuals and not classes is the cladistic species concept. The cladistic species concept defines species as the group of organisms between two speciation events, or between one speciation event and one extinction event, or (for living species) that are descended from a speciation event. It is a theoretical concept, and therefore has the virtue of distinguishing clearly the theoretical nature of species from the practical criteria by which species may be (...) recognized at any one time. Ecological or biological (reproductive) criteria may help in the practical recognition of species. Ecological and biological species concepts are also needed to explain why cladistic species exist as distinct lineages, and to explain what exactly takes place during a speciation event. The ecological and biological species concepts work only as sub-theories of the cladistic species concept and if taken by themselves independently of cladism they are liable to blunder. The biological species concept neither provides a better explanation of species indivudualism than the ecological species concept, nor, taken by itself, can the biological species concept even be reconciled with species individualism. Taking the individuality of species seriously requires subordinating the biological, to the cladistic, species concept. (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)

Biological racial realism (BRR) continues to be a much-discussed topic, with several recent papers presenting arguments for the plausibility of some type of “biological race.” In this paper, the focus will be on the phylogenetic conceptions of race, which is one of the most promising views of BRR, that define races as lineages of reproductively isolated breeding populations. However, I will argue that phylogenetic conceptions of race fail to prove that races are biologically real. I will develop and defend my (...) argument against the phylogenetic views of race by relying on current research in population genetics, human evolution, and social sciences. Ultimately, I will argue that (i) race is not a biologically legitimate category and (ii) philosophers should direct their resources to understand problems that arise due to racialization, and thereby they should find solutions to those problems. (shrink)

Ontological understanding of biological units is crucial to their use in experimental design, analysis, and interpretation. Conceptualizing fundamental units in biology as individuals or classes is important for subsequent development of discovery operations. While the criteria for diagnosing individuals are acknowledged, temporal boundedness is often misinterpreted and temporal minima are applied to units in question. This results in misdiagnosis or abandonment of ontological interpretation altogether. Biological units such as areas of endemism in biogeography and species in evolutionary biology fall victim (...) to such problems. Our goal here is to address the misconception that biological individuals such as species and areas of endemism have a temporal minimum. Areas of endemism can persist within small temporal boundaries in the context of metapopulation dynamics, island biogeography, and range expansion and contraction. Similarly, lineage reticulation illustrates examples of short-lived species. Here, examples of known entities are provided to illustrate their persistence on short time scales in attempt to rescue future interpretation of biological units from ontological misdiagnosis, elucidate the philosophical individuality of areas of endemism and species with short lifespans, and provide justification for the “snapshot in time” diagnostic approach. (shrink)

College of Medicine, University of South Alabama Mobile, AL 36688-0002, USA wbp501{at}jaguar1.usouthal.edu ' + u + '@' + d + ' '//--> Abstract Recent work in viral genomics has shown that bacteriophages exhibit a high degree of mosaicism, which is most likely due to a long history of prolific horizontal gene transfer (HGT). Given these findings, we argue that each of the most plausible attempts to properly classify bacteriophages into distinct species fail. Mayr's biological species concept fails because there is (...) no useful viral analog to sexual reproduction. Phenetic species concepts fail because they obscure the mosaicism and the rich reticulated viral histories. Phylogenetic species concepts, even when extended to take into account reticulation, fail because there is no non-arbitrary distinction between recombination events that create a new viral species and those that do not. There is good reason to think that bacteriophages, arguably the Earth's most abundant biological agent, evolve without forming species. Introduction The Biology of Viruses 2.1 Bacteriophage life cycles 2.2 Mechanisms of HGT The Species Problem and Species Concepts 3.1 Phenetic species concepts 3.2 The biological species concept 3.3 Phylogenetic species concepts 3.4 The ecological species concept 3.5 Homeostatic property cluster species Viruses and Species Taxonomy Reticular Phylogenies Conclusion CiteULike Connotea Del.icio.us What's this? (shrink)

The concept of individuality as applied to species, an important advance in the philosophy of evolutionary biology, is nevertheless in need of refinement. Four important subparts of this concept must be recognized: spatial boundaries, temporal boundaries, integration, and cohesion. Not all species necessarily meet all of these. Two very different types of pluralism have been advocated with respect to species, only one of which is satisfactory. An often unrecognized distinction between grouping and ranking components of any species concept is necessary. (...) A phylogenetic species concept is advocated that uses a grouping criterion of monophyly in a cladistic sense, and a ranking criterion based on those causal processes that are most important in producing and maintaining lineages in a particular case. Such causal processes can include actual interbreeding, selective constraints, and developmental canalization. The widespread use of the biological species concept is flawed for two reasons: because of a failure to distinguish grouping from ranking criteria and because of an unwarranted emphasis on the importance of interbreeding as a universal causal factor controlling evolutionary diversification. The potential to interbreed is not in itself a process; it is instead a result of a diversity of processes which result in shared selective environments and common developmental programs. These types of processes act in both sexual and asexual organisms, thus the phylogenetic species concept can reflect an underlying unity that the biological species concept can not. (shrink)

Recent and ongoing debates in biology and in the philosophy of biology reveal widespread dissatisfaction with the current definitions or circumscriptions, which are often vague or controversial, of key concepts such as the gene, individual, species, and homology, and even of whole disciplinary fields within the life sciences. To some extent, the long growing awareness of these conceptual issues and the contrasting views defended in their regard can be construed as a symptom of the need to revisit traditional unchallenged partitions (...) between the specialist disciplines within the life sciences. I argue here that the current relationships between anchor disciplines (e.g., developmental biology, evolutionary biology, biology of reproduction) and nomadic concepts wandering between them is worth being explored from a reciprocal perspective, by selecting suitable anchor concepts around which disciplinary fields can flexibly move. Three examples are offered, focusing on generalized anchor concepts of generation (redefined in a way that suggests new perspectives on development and reproduction), organizational module (with a wide-ranging domain of application in comparative morphology, developmental biology, and evolutionary biology) and species as unit of representation of biological diversity (suggesting a taxonomic pluralism that must be managed with suitable adjustments of current nomenclature rules). (shrink)

What are biological species? Aristotelians and Lockeans agree that they are natural kinds; but, evolutionary theory shows that neither traditional philosophical approach is truly adequate. Recently, Michael Ghiselin and David Hull have argued that species are individuals. This claim is shown to be against the spirit of much modern biology. It is concluded that species are natural kinds of a sort, and that any 'objectivity' they possess comes from their being at the focus of a consilience of inductions.

The continuing discussion of the species problem suffers from the lack of a coherent ontological theory as a basis for determining whether species have an ontological status. It has attempted to apply a full-fledged metaphysical theory to the species problem: the ontology of Mario Bunge. In doing so a few ontological fundamentals including system, individual, real and conceptual object, and law are briefly introduced. It is with the help of these fundamentals that an analysis of the species-as-individuals thesis is carried (...) out, concluding that species are not individuals (things), but natural kinds, and that they have no ontological status. In contradistinction to the traditional view of natural kinds involving possible worlds metaphysics and semantics a notion of natural kind is given in terms of the state space approach and of nomological equivalence. (shrink)

The continuing discussion of the species problem suffers from the lack of a coherent ontological theory as a basis for determining whether species have an ontological status. It has attempted to apply a full-fledged metaphysical theory to the species problem: the ontology of Mario Bunge. In doing so a few ontological fundamentals including system, individual, real and conceptual object, and law are briefly introduced. It is with the help of these fundamentals that an analysis of the species-as-individuals thesis is carried (...) out, concluding that species are not individuals (things), but natural kinds, and that they have no ontological status. In contradistinction to the traditional view of natural kinds involving possible worlds metaphysics and semantics a notion of natural kind is given in terms of the state space approach and of nomological equivalence. (shrink)

The aim of this article is to illustrate how a belief in the existence of kinds may be justified for the particular case of natural kinds: particularly noteworthy in this respect is the weight borne by scientific natural kinds (e.g., physical, chemical, and biological kinds) in (i) inductive arguments; (ii) the laws of nature; and (iii) causal explanations. It is argued that biological taxa are properly viewed as kinds as well, despite the fact that they have been by some alleged (...) to be individuals. Since it turns out that the arguments associated with the standard Kripke/Putnam semantics for natural kind terms only establish the non-descriptiveness of natural kind terms and not their rigidity, the door is open to analyze these terms as denoting traditional predicate-extensions. Finally, special issues raised by physical and chemical kinds are considered briefly, in particular impurities, isotopes and the threat of incommensurability. (shrink)

The species category is defined as thesmallest historical individual within which there is a parental pattern of ancestry and descent. The use of historical individual in this definition is consistent with the prevailing notion that speciesper se are not involved in processes — they are effects, not effectors. Reproductive isolation distinguishes biparental historical species from their parts, and it provides a basis for understanding the nature of the evidence used to discover historical individuals.

The Empiricist or Lockean view says natural kinds do not exist objectively in nature but are practical categories reflecting use of words. The Modern, Ostensive view says they do exist, and one can refer to such a kind by ostention and recursion, assuming his designation of it is related causally to the kind itself. However, this leads to a problem: Kinds are abstract repeatables, and it seems impossible that abstractions could have causal force. In defence of the Modern view, I (...) suggest we can think of kinds as — or as like — ecological niches existing in nature, which are causally effective by virtue of the fact that they predictively determine (some) properties of the things that happen to occupy them. (shrink)

Although naming biological clades is a major activity in taxonomy, little attention has been paid to what these names actually refer to. In philosophy, definite descriptions have long been considered equivalent to the meaning of names and biological taxonomy is a scientific application of these ideas. One problem with definite descriptions as the meanings of names is that the name will refer to whatever fits the description rather than the intended individual (clade). Recent proposals for explicit phylogenetic definitions of clade (...) names suffer from similar problems and we argue that clade names cannot be defined since they lack intension. Furthermore we stress the importance of tree-thinking for phylogenetic reference to work properly. (shrink)

The subject of this paper is the integrity of nature over time—‘diachronic integrity’. The argument of the parer is that any serious attempt to address conservation problems—the kinds of problems faced by environmental managers the world over, needs to operate with an eye to some principle of diachronic integrity. Whilst acknowledging that applying the principle is largely a matter of experience and judgement, we argue that it applies equally both to human and to natural history.

ABSTRACT Summed up in the coinage of the term ‘pre‐embryo’is the denial that human beings, as such, begin to exist from the moment of conception. This denial, which may be thought to have significant moral implications, rests on two kinds of reason. The first is that the pre‐embryo lacks the characteristics of a human being. The second is that the pre‐embryo lacks what it takes to be an individual human being. The first reason, I argue, embodies an untenable view of (...) what it is to be human. The second reason exploits certain logical difficulties which arise over the possibility of twinning. I question the relevance of the appeal to such difficulties and conclude that there is no good reason for denying that a human being begins to exist from the moment of conception. (shrink)

Although generally informed by an intimate knowledge of evolutionary biology and taxonomy, the controversy over the nature of species is clearly philosophical; it consists almost entirely of the clarification of old, and the invention of new arguments for or against calling the species category a class, The debate seems firmly divided between those, like Kitts and Bernier, who see homo sapiens as a class, and those, like Hull and Ghiselin, who see it as an individual. In the first case, particular (...) human beings are members; in the second case, parts. To the champions of class, the essentialists, each species can be defined by means of a unique set of necessary and sufficient conditions, and every organism can be placed without equivocation into a particular species. To the individualists, nothing could be further from the truth. As a contingent, product of evolution, each species shares that crucial characteristic of an individual, spacio-temporal identity; each is a chunk of genealogical nexus. (shrink)

The idea of naturalizing metaphysics stretches back to Locke and Newton. Recently it has been revived by Ross and Ladyman et al (2007) in ‘Every Thing Must Go’. At the heart of the doctrine is the idea that metaphysics should be constrained by actual science (science which is current and institutionally valid). It is my attempt in this paper to naturalize the metaphysics of the species problem by proposing a species concept which conforms to the principles set out in Ross (...) and Ladyman et al's book. This is a concept which conforms strictly with current work in the field of evolutionary theory, with specific reference to theories in Information theory and Thermodynamics. In the end I use as an example of non-naturalized metaphysics Matthew Slater's paper ‘The Indeterminacy Problem for Species as Individuals’. (shrink)

Since the 1970s, there has been a tremendous amount of literature on Ghiselin's proposal that species are individuals. After recalling the origins and stakes of this thesis in contemporary evolutionary theory, I show that it can also be found in the writings of the French naturalist Buffon in the 18th Century. Although Buffon did not have the conception that one species could be derived from another, there is an interesting similarity between the modern argument and that of Buffon regarding the (...) individuality of species. The analogy is strong enough to force us to recognize that genuine evolutionary (or Darwinian) questions might be of secondary importance in the discussion. In consequence, the third section of the paper proposes an alternative schema for the logical structure of the Darwinian concept of species. Darwin distinguished the problem of the designation of a concrete species, and the problem of its signification of species within his theory of descent? The resulting notion of species involves a logical structure based on the fusion of the logical operations of classification and ordering. The difficulty — and interest — is that this interpretation of species does not entail any precise operational definition of species; it can only tell us what the ultimate signification of classification is within the theory of descent with modification through natural selection. (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)

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.

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.

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.

The issue of whether species are individuals is now an old one; the literature abounds with arguments, counter-arguments and counter-counter-arguments for their individuality. The question I want to take up in this paper is not whether species are indeed individuals, but what ramifications their alleged individuality has for macroevolutionary theory.According to those biologists who argue for a new theory of macroevolution, the individuality of species is one of the fundamental premises of that theory. For example, Joel Cracraft writes of himself (...) and others thatThe issue of individuality… is at the heart of arguments of those evolutionary biologists who see a need to view the patterns and processes of evolution as being hierarchically arranged into microevolutionary and macroevolutionary levels (1987, p. 332). (shrink)

Biologists and philosophers that debate the existence of the species category fall into two camps. Some believe that the species category does not exist and the term 'species' should be eliminated from biology. Others believe that with new biological insights or the application of philosophical ideas, we can be confident that the species category exists. This paper offers a different approach to the species problem. We should be skeptical of the species category, but not skeptical of the existence of those (...) taxa biologists call 'species.' And despite skepticism over the species category, there are pragmatic reasons for keeping the word 'species.' This approach to the species problem is not new. Darwin employed a similar strategy to the species problem 150 years ago. (shrink)