When developing phylogenetic systematics, the entomologist Willi Hennig adopted elements from Nicolai Hartmann’s ontology. In this historical essay I take on the task of documenting this adoption. I argue that in order to build a metaphysical foundation for phylogenetic systematics, Hennig adopted from Hartmann four main metaphysical theses. These are (1) that what is real is what is temporal; (2) that the criterion of individuality is to have duration; (3) that species are supra-individuals; and (4) that there are levels of (...) reality, each of which may be subject to different kinds of law. Reliance on Hartmann’s metaphysics allowed Hennig to ground some of the main theoretical principles of phylogenetic systematics, namely that the biological categories—from the semaphoront to the highest rank—have reality and individuality despite not being universals, and that they form a hierarchy of levels, each of which may require different kinds of explanation. Hartmann’s metaphysics thereby provided a philosophical justification for Hennig’s phylogenetic systematics, both as a theory and as a method of classification. (shrink)

Taxa and homologues can in our view be construed both as kinds and as individuals. However, the conceptualization of taxa as natural kinds in the sense of homeostatic property cluster kinds has been criticized by some systematists, as it seems that even such kinds cannot evolve due to their being homeostatic. We reply by arguing that the treatment of transformational and taxic homologies, respectively, as dynamic and static aspects of the same homeostatic property cluster kind represents a good perspective for (...) supporting the conceptualization of taxa as kinds. The focus on a phenomenon of homology based on causal processes (e.g., connectivity, activity-function, genetics, inheritance, and modularity) and implying relationship with modification yields a notion of natural kinds conforming to the phylogenetic-evolutionary framework. Nevertheless, homeostatic property cluster kinds in taxonomic and evolutionary practice must be rooted in the primacy of epistemological classification (homology as observational properties) over metaphysical generalization (series of transformation and common ancestry as unobservational processes). The perspective of individuating characters exclusively by historical-transformational independence instead of their developmental, structural, and functional independence fails to yield a sufficient practical interplay between theory and observation. Purely ontological and ostensional perspectives in evolution and phylogeny (e.g., an ideographic character concept and PhyloCode’s ‘individualism’ of clades) may be pragmatically contested in the case of urgent issues in biodiversity research, conservation, and systematics. (shrink)

The formal definition of species as explanatory hypotheses presented by Fitzhugh is emended. A species is an explanatory account of the occurrences of the same character among gonochoristic or cross-fertilizing hermaphroditic individuals by way of character origin and subsequent fixation during tokogeny. In addition to species, biological systematics also employs hypotheses that are ontogenetic, tokogenetic, intraspecific, and phylogenetic, each of which provides explanatory hypotheses for distinctly different classes of causal questions. It is suggested that species hypotheses can not be applied (...) to organisms with obligate asexual, parthenogenetic, and self-fertilizing modes of reproduction. Hypotheses explaining shared characters among such organisms are, instead, strictly phylogenetic. Several implications of this emended definition are examined, especially the relations between species, intraspecific, and phylogenetic hypotheses, as well as the limitations of species names to be applied to temporally different characters within populations. (shrink)

Essentialism is widely regarded as a mistaken view of biological kinds, such as species. After recounting why (sections 2-3), we provide a brief survey of the chief responses to the “death of essentialism” in the philosophy of biology (section 4). We then develop one of these responses, the claim that biological kinds are homeostatic property clusters (sections 5-6) illustrating this view with several novel examples (section 7). Although this view was first expressed 20 years ago, and has received recent discussion (...) and critique, it remains underdeveloped and is often misrepresented by its critics (section 8). (shrink)

The relatively late acceptance of Darwinism in German biology and paleontology is frequently attributed to a lingering of Lamarckism, a persisting influence of German idealistic Naturphilosophie and Goethean romanticism. These factors are largely held responsible for the vitalism underlying theories of saltational and orthogenetic evolutionary change that characterize the writings of many German paleontologists during the first half of the 20th century. A prominent exponent of that tradition was Karl Beurlen, who is credited with having been the first German paleontologist (...) to present a full-fledged theory of saltational evolution and orthogenetic change. A review of Beurlen's writings reveals motives and concerns far more complex, however, and firmly rooted in contemporary völkisch thought and Aryan Science. Beurlen's mature theory of evolution can indeed be understood as his own contribution to Aryan Geology and Biology, tainted as it was with National-Socialist ideology. Evolutionary biologists of the time who opposed the theories of Beurlen and likeminded authors, i.e., idealistic morphology, typology, saltational change, orthogenesis and cyclism did so on Darwinian principles, which ultimately prevailed. But at the time when the battle was fought, their adherence to the principle of natural selection was likewise ideologically tainted, namely in terms of racial theory. National-Socialist ideology was unable to forge a unity of evolutionary theory in Germany even amongst those of its proponents who endorsed this ideology. (shrink)

This paper takes a hierarchical approach to the question whether species are individuals or natural kinds. The thesis defended here is that species are spatiotemporally located complex wholes (individuals), that are composed of (i.e., include) causally interdependent parts, which collectively also instantiate a homeostatic property cluster (HPC) natural kind. Species may form open or closed genetic systems that are dynamic in nature, that have fuzzy boundaries due to the processual nature of speciation, that may have leaky boundaries as is manifest (...) in lateral gene transfer and introgression, that may be of multiple origins through hybridization, and that may split and merge and split again over time. The identity conditions of species qua individuals will have to be anchored in their history, rather than in their unique evolutionary origin. Species qua historically conditioned HPC natural kinds requires the kind to be mereologically structured, subject to the part-whole relation rather than the membership relation. This implies that there can be more than one kind of natural kinds. (shrink)

The aim of this article is to detail some reservations against the beliefs, claims, or presuppositions that current essentialist natural kind concepts (including homeostatic property cluster kinds) model grouping practices in the life sciences accurately and generally. Such concepts fit reasoning into particular preconceived epistemic and semantic patterns. The ability of these patterns to fit scientific practice is often argued in support of homeostatic property cluster accounts, yet there are reasons to think that in the life sciences kind concepts exhibit (...) a diversity of grouping practices that are flattened out by conceptualizing them as natural kinds. Instead this article argues that the process of understanding grouping practices needs to start from a more neutral position independent of any ontological account. Following Love (Acta Biotheor 57:51–75, 2009) this paper suggests that typical natural kind concepts should be broached in the first place as grouping strategies that use a variety of semantic and epistemic tactics to apply group-bound information to tasks of explanation and understanding. (shrink)

This article, which is intended both as a position paper in the philosophical debate on natural kinds and as the guest editorial to this thematic issue, takes up the challenge posed by Ian Hacking in his paper, “Natural Kinds: Rosy Dawn, Scholastic Twilight.” Whereas a straightforward interpretation of that paper suggests that according to Hacking the concept of natural kinds should be abandoned, both in the philosophy of science and in philosophy more generally, we suggest that an alternative and less (...) fatalistic reading is also possible. We argue that abandoning the concept of natural kinds would be premature, as it still can do important work. Our concern is with the situation in the (philosophy of the) life sciences. Against the background of this concern we attempt to set something of an agenda for future research on the topic of natural kinds in the (philosophy of the) life sciences. (shrink)

Despite the traditional focus on metaphysical issues in discussions of natural kinds in biology, epistemological considerations are at least as important. By revisiting the debate as to whether taxa are kinds or individuals, I argue that both accounts are metaphysically compatible, but that one or the other approach can be pragmatically preferable depending on the epistemic context. Recent objections against construing species as homeostatic property cluster kinds are also addressed. The second part of the paper broadens the perspective by considering (...) homologues as another example of natural kinds, comparing them with analogues as functionally defined kinds. Given that there are various types of natural kinds, I discuss the different theoretical purposes served by diverse kind concepts, suggesting that there is no clear-cut distinction between natural kinds and other kinds, such as functional kinds. Rather than attempting to offer a unique metaphysical account of ‘natural’ kind, a more fruitful approach consists in the epistemological study of how different natural kind concepts are employed in scientific reasoning. (shrink)

Species are central to biology, but there is currently no agreement on what the adequate species concept should be, and many have adopted a pluralist stance: different species concepts will be required for different purposes. This thesis is a multidimensional analysis of species pluralism. First I explicate how pluralism differs monism and relativism. I then consider the history of species pluralism. I argue that we must re-frame the species problem, and that re-evaluating Aristotle's role in the histories of systematics can (...) shed light on pluralism. Next I consider different forms of pluralism: evolutionary and extra-evolutionary species pluralism, which differ in their stance on evolutionary theory. I show that pluralism is more than a debate about the species category, but a debate about which concepts are legitimate and a claim about how they interact with one another. Following that, I consider what sort of ontology is required for different forms of species pluralism. I argue that pluralists who deny the unity of biology will require a further plurality of frameworks, while those that ground their pluralism in evolution need only one framework. Finally, I consider what pluralism means for biological practice. I argue that species concepts are tools, and reflect on how pluralism can illuminate the way systematists approach the discovery of new species of yeast. Pluralism can make sense of the way species concepts are used, and can be developed to aid researchers in thinking about how to use the right tools for the right jobs. (shrink)

The German synthesis of evolutionary theory that grew out of opposition to idealistic morphology has been anchored in the systematic work at the species level and below pursued by the Berlin School around Erwin Stresemann (involving Bernhard Rensch and Ernst Mayr), in the 1939 German translation of Dobzhansky’s Genetics and the Origin of Species, and in a 1943 anthology on evolution edited by Gerhard Heberer. The latter volume opened with a philosophical essay written by Hugo Dingler that was intended to (...) provide the theoretical foundation for the theory of descent. Dingler and Heberer not only shared a commitment to the Darwinian evolutionary mechanisms of random mutation and natural selection, but also drew from Darwinism the justification for racial hygiene and eugenics. Dingler’s “unequivocal-methodological system” is a meta-scientific construct that offers no ontological grounding of evolutionary theory. Dingler’s voluntarism is subjectivist and stipulative and for those reasons ineffective in a critique of idealistic morphology. Dingler claimed descent with modification as a historical fact, but dealt only marginally with evolutionary mechanisms, and did not touch on issues of phylogeny reconstruction. (shrink)

Species pluralism allows for multiple species concepts. Given the overwhelming number of such concepts, this seems like an obvious interpretation of how `species' is used in contemporary biology. But why has it taken so long for this approach to be considered? I argue that part of the reason pluralism was overlooked due to the widespread use of a particular rhetorical strategy developed by Ernst Mayr. This strategy provided a framework for debates about the correct conception of species. That is, the (...) strategy offered a means of comparing modern concepts with a monistic-essentialist understanding of species. I ask what would happen if we replaced this concept with Aristotle's own pluralist-essentialist understanding of species. As recent scholarship shows, Aristotle's philosophy of biology allows for an approach to classification that is in practice highly pluralistic. From this new framework we can understand what sort of assumptions are at stake between modern forms of species pluralism. My analysis shows that the essentialist story told by Mayr and others left us asking the wrong questions about how to conceive of species in an evolutionary world. Having a deeper understanding of Aristotle's approach to the classification of animals allows us to shift focus from the so-called species problem in order to raise four issues that are relevant to current debates. These are questions about: the explanatory power of taxonomic ranks, the importance of the species category problem, whether species are constituted by intrinsic or extrinsic properties, and how to interpret the ``cross-cutting'' metaphor endemic to the pluralist literature. In order to get to these questions I will first explain what sort of claim species pluralism is at the most general level, and a gloss on the standard interpretation of the historical shift from species monism to species pluralism. (shrink)

The history of biological systematics documents a continuing tension between classifications in terms of nested hierarchies congruent with branching diagrams (the ‘Tree of Life’) versus reticulated relations. The recognition of conflicting character distribution led to the dissolution of the scala naturae into reticulated systems, which were then transformed into phylogenetic trees by the addition of a vertical axis. The cladistic revolution in systematics resulted in a representation of phylogeny as a strictly bifurcating pattern (cladogram). Due to the ubiquity of character (...) conflict—at the genetic or morphological level, or at any level in between—some characters will necessarily have to be discarded ( qua noise) in favor of others in support of a strictly bifurcating phylogenetic tree. Pattern analysts will seek maximal congruence in the distribution of characters (ultimately of any kind) relative to a branching tree-topology; process explainers will call such tree-topologies into question by reference to incompatible evolutionary processes. Pattern analysts will argue that process explanations must not be brought to bear on pattern reconstruction; process explainers will insist that the reconstructed pattern requires a process explanation to become scientifically relevant, i.e., relevant to evolutionary theory. The core question driving the current debate about the adequacy of the ‘Tree of Life’ metaphor seems to be whether the systematic dichotomization of the living world is an adequate representation of the complex evolutionary history of global biodiversity. In ‘Questioning the Tree of Life’, it seems beneficial to draw at least four conceptual distinctions: pattern reconstruction versus process explanation as different epistemological approaches to the study of phylogeny; open versus closed systems as expressions of different kinds of population (species) structures; phylogenetic trees versus cladograms as representations of evolutionary processes versus patterns of relationships; and genes versus species as expressions of different levels of causal integration and evolutionary transformation. (shrink)