Homage to Metaphysics: Post-Positivist Revolution

In the middle and second half of the 20th century, the “historical pendulum” in the development of natural science begins to move in the opposite direction. The influence of positivist (first of all, physicalist) ideas, putting a hard boundary between “science” and “stamp collecting” and founding all natural science on a reductionist counter-metaphysical basis, is noticeably weakening. Instead, the ideas of the post-positivist philosophy of science come to the fore, forming the basis of its non-classical cognitive paradigm [Popper 1959; Kuhn 1962; Lakatos 1978; Quine 1996; Ilyin 2003; Stepin 2005]. An understanding emerges that the general cognitive situation of natural science is structured much more complexly than is assumed by both the classical and positivist philosophies of science. With this, a key place in its ontology is given to a rather rich scientific metaphysics shaping the background knowledge of natural science research. Besides, scientific pluralism is proclaimed, according to which cognitive activity in science is structured by particular research programs and paradigms interacting in a complex way. The fundamental cognitive status of the diversity of biological phenomena, which is in no way inferior to the search for unifying laws and constants, is acknowledged [Rosenberg 1985; Mayr 1988; Chebanov 2016]. This results in a revival of interest in the Natural System as a manifestation of general regularities supposedly occurring in the structured diversity of any natural phenomena [Rozova 1980, 1986; Tchaikovsky 1990; Rozov 1995].

Discussion of new ideas of onto-epistemic foundations of natural science, with a return of interest in metaphysics and respective loss of interest in positivist elementarism, has a noticeable impact on theoretical systematics and marks the beginning of a new' phase in its conceptual history. Biological systematics begins to return to its former prestige and gradually frees itself from the “Cinderella syndrome” [Rosenberg 1985]. This leads to a loss of attractiveness of the research programs that emerged in the context of the positivist paradigm (phenetics, partly biosystematics), and creates certain preconditions for a revival of interest in the macro-scale historical and structural manifestations of taxonomic diversity. According to how philosophers of science call the new cognitive paradigm, this shift of systematics in a new direction can be designated as a post-positivist revolution, the last (at the present moment) in its conceptual history [Pavlinov 2019]. From the conceptual historical perspective, its main content is substantive, so it does not include the above-mentioned “technological” revolution continuing the physicalist trend.

At a philosophical scientific level, it is important, although hardly fully realized so far, that this revolution, generated by the influence of the non-classical scientific paradigm, stimulated the beginning of the formation of a non-classical frame for systematics [Pavlinov 2006, 2013b, 2018]. It legitimizes not only metaphysics as an important part of the cognitive situation of this discipline, but also taxonomic pluralism as an inevitable consequence of the diversification trend in its conceptual history.

Among particular research programs that begin to develop most actively in the context of the post-positivist history of systematics, phylogenetics in its new guise occupies first place. It is shaped by a combination of three independently emerging components, viz. cladistic methodology, molecular factual basis, and numerical technology. Together, they shape the new phylogenetics [Pavlinov 2003, 2005]; its taxonomic application suggests the name genosystematics [Mednikov 1980; Antonov 2006]. The changes it makes in practical systematics are so significant that they are sometimes equated with a scientific revolution [de Queiroz 1988], which is called cladogenetic [Pavlinov 2019,2020]. However, this “revolution” is not so much a conceptual as a technological one, connected with the development of new approaches to phylogenetic reconstruction; therefore, in this book its formation is presented as part of the post-positivist revolution.

The basic ideas of a cladistic version of phylogenetics were foreseen by C. Darwin (see Section 2.5.1), and in the 20th century they are formalized by the botanist Walter Zimmermann and the zoologist Willie Hennig [Zimmermann 1931, 1934; Hennig 1950, 1966]; from the 1970s, it becomes increasingly popular, and manuals are published one after another [Nelson and Platnick 1981; Wiley 1981; Ax 1987; Shatalkin 1988; Pavlinov 1990, 2005; Wagele 2005; Williams and Ebach 2008]. This version differs from Haeckel’s mainly by a refined theoretical and operational definition of monophyly. This refinement is supplemented by a proposal to classify only strictly monophyletic (holophyletic) groups, which causes the radical restructuring of many “classical” phylogenetic classifications. The molecular component of the new phylogenetics is developed by phylogenomics (genophyletics): it gives the greatest importance to DNA and RNA macromolecules and ignores other organismal features, so it is a version of the above-mentioned chemosystematics. It is of importance that molecular genetic data remove many restrictions that did not previously allow analysis of the diversity of prokaryotes and their direct comparison with eukaryotes, so an idea of the global “Tree of Life” is revived, now built on a unified molecular basis [Cracraft and Donoghue 2004]. An active development of the numerical component of the “new phylogenetics” is predetermined by its cladistic and molecular genetic components. Numerical phenetics and phyletics develop almost synchronously in the

1960s-1970s in acute competition, but numerical phyletics wins this “struggle for existence” [Hull 1988] and now dominates in taxonomic research. Inspired by this, the statistician Joseph Felsenstein, one of the leaders of molecular phyletics, announces in a somewhat joking manner that he “founded the fourth great school of classification, the It-Doesn’t-Matter-Very-Much school” [Felsenstein 2004: 145]; its methods are considered in a number of manuals [Hillis et al. 1996; Nei and Kumar 2000; Felsenstein 2004; Albert 2005]. With this, the methodology of this “great school” is largely guided by the same reductionist positivist philosophy that earlier gave rise to numerical phenetics, so “de-physicalization” of the most recent sytematics appears to be only partial [Pavlinov 2018, 2019].

A shift from a classical to cladogenetic version of phylogenetics provides an interesting example of the so-called "butterfly effect” in the conceptual history of systematics. Indeed, it begins with just a narrower definition of the monophyletic group as the only allowable element of the phylogenetic classification. Then it becomes enthusiastically accepted and massively applied by phylogeneticists of the new generation. This leads to significant changes in most traditional phylogenetic classifications, at first without any “molecular” interference.

In the recent conceptual history of systematics, a noticeable place is occupied by structuralist theories that gravitate towards typology in its various manifestations; they compose onto-rational systematics [Pavlinov 2011b, 2018; Pavlinov and Lyubarsky 2011]. The latter is aimed at uncovering structural causes of the morphological disparity of organisms; its basic task is to identify law-like regularities in this disparity and to present them in the form of natural classifications of their own.

At present, it is realized that “cladogenetic revolution” in systematics appears to be too radical and this leads to its significant “de-biologization.” In this regard, an impression arises that a new revolution in systematics is slowly brewing, promising a post-cladistic stage in its conceptual history [Wheeler 2008; Williams and Knapp 2010; Zander 2013; Pavlinov 2019, 2020]. Its driving force seems to be a very interesting research program, which begins to emerge within the framework of evolutionary interpreted systematics. It links the structural consideration of the disparity of organisms with evolutionary developmental biology (“evo-devo”) [Minelli 2015; Pavlinov 2019, 2020], which focuses on the evolution of epigenetic regulators of ontogenetic patterns [Minelli 2003; Minelli and Pradeu 2014]. This program, in its own evolutionary way, revives a significant element of epigenetic typology and provides a new stimulus for the development of the above-mentioned ontogenetic systematics. Whether or not this revolution will happen and whether it will actually lead to the emergence of a new research program of evolutionary’ ontogenetic systematics remains to be seen (see Section 5.8).

Currently, however, a new and more practical challenge seems to rise that may seriously affect the nearest future of biological systematics. It is caused by a certain gap between the needs of the biodiversity issues and the capabilities of biological systematics, which is designated as “taxonomic impediment" (e.g„ [Godfray 2002; Wheeler et al. 2004; Agnarsson and Kuntner 2007; de Carvalho et al. 2007; Raposo et al. 2020]; etc.). It remains just to guess at the moment what might be its consequences for the conceptual development of systematics to make it another “new” one.

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