Philosophy of biology

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The philosophy of biology (also biophilosophy ) is a branch of the philosophy of science . Topics in the philosophy of biology are the philosophical prerequisites, conditions and evaluations of biological theory formation, experimental research and applications. In addition to the methods of an analytical theory of science, the philosophy of biology also includes theories of the history of science and the sociology of science.

In a broader sense, the philosophy of biology also discusses how models and methods from biology influence more general topics of philosophy; for example with the concept of evolutionary epistemology , in which the principle of biological evolution is applied to the structure and possibility of knowledge . The growing importance of biological disciplines such as genetic engineering or molecular biology and their increasing use of technology and economization in recent decades has also led to countless and ongoing ethical problems and debates. The same applies to ecology , which has gained broad social importance in the context of nature conservation. Biology, with its diverse subject areas and methods, is also partially considered to be the future pluralistic “leading discipline” and “ science of the century” and as such is intended to replace physics and physicalism . The transitions from the philosophy of biology to theoretical biology and neurophilosophy are fluid.

meaning

The philosophy of biology is involved in many cases in clarifying and solving research questions in biology with practical relevance. In addition to general problems in the theory of science, it is often about clarifying the points of view, theories and terms within biology, but also about controversies about the social effects of biological knowledge and technologies.

In the second half of the 20th century, the philosophy of biology received a great surge in importance, which is justified by the scientific and technical development in biology, but also in the development of society. The nature conservation debate and the emergence of the discussion about the correct relationship to ecology drew attention to the question of anthropogenic influences on natural occurrences. The mechanization and economization of biology in biotechnology and genetic engineering , on the other hand , calls for ethical , ontological and epistemological answers. And finally, the results of neurobiology pose new questions about technical applicability and about the image of man within biology.

Philosophers who deal with biological subjects are often also biologists who have trained themselves. Several biologists such as Ernst Mayr , Richard Dawkins, and Michael Ghiselin have also made significant contributions to the philosophy of biology. Since 1985 the journal " Biology und Philosophy " has been published.

The philosophy of biology concentrated for a long time on evolutionary biology and the status of organisms and rather neglected the physico-chemical branches of biology such as molecular biology . On the other hand, the philosophy of biology enriches wide areas of philosophy itself in a variety of ways. In contrast, the technical and physical-chemical disciplines and their philosophical reflection are in most cases already covered by more general scientific theoretical work. Concepts and conditions in biology that differ from general epistemological questions are, for example, the duality of phenotype and genotype , the historical element, the uniqueness and the diverse organization and complexity of many objects of investigation, but also the concept of life itself, teleology ( functional purpose) and natural selection . After physics, and especially mechanics , have shaped the models and methods of the philosophy of science for centuries, the question now arises as to what status biology has in the philosophy of science. This question and the answers to it concern all areas of dealing with biology and ultimately also questions of logic , methodology and concrete research practice.

The philosophy of biology mostly focuses on the reflection of biological terms, theories and methods - that is, the work of philosophers to successfully deal with the content of biological research. Conversely, many influences on more general topics and areas of philosophy have become clear through this occupation. The best-known examples are evolutionary epistemology for epistemology, bioethics , but also an essential part of current anthropological topics. Biophilosophy with its pluralistic, ecological and historical approaches also poses challenges to the philosophy of science and the ideal of a standardized science .

history

Aristotle is considered to be the "founder" of the philosophy of biology - and also of zoology . His philosophy shaped western thinking about organisms, their parts and their organization up to modern times. With Aristotle, the unmoved things are excluded from “natural things”; they are the object of theology . Likewise, created works of art and irregular, i.e. random events are not natural for Aristotle and therefore not an object of his physics. According to Aristotle, organisms are organized bodies, which on the one hand are differentiated into organs and on the other hand are connected by their functions. The form of the body is its soul (see also entelechy ) and is therefore neither independent nor inseparable from the body. Functions of the soul are for example eating, breathing, growing and sleeping. With the help of a valuable hierarchy of these functions, he can create a "step ladder of nature" ( Scala Naturae ) and thus a systematics across all living beings and beyond. It is also the soul that determines a purpose for every living being . As a Causa finalis (final cause) it works directly in the direction of a self-realization of the individual. Aristotle anchors the cosmological teleological principle of Plato in the concrete organism and thus in nature. Whether one can therefore speak of “teleology” in the case of Aristotle is judged differently in the philosophy of biology.

Jacques de Vaucanson's mechanical duck , inspired by the mechanistic understanding of the body

Aristotelian thinking was largely formative for Western philosophy. In particular, the principle of the final cause was adopted by the Christian theologians and developed into a proof of God . It was only with the mechanistic thinking of the early modern period that the teleological approach was displaced, as it was hardly accessible to the newly emerging scientific method. Another departure from Aristotle was the very influential dualistic separation in body and mind of René Descartes . Everything that was not (human) spirit was henceforth "body" and thus accessible to the same scientific method. The divisions that Aristotle's soul functions established between living beings and the non-living world became meaningless. In the wake of mechanistic thinking, many discussions revolved around the question of how the apparently obvious otherness of living beings could still be explained.

Immanuel Kant was a keen observer of biological research of his time . He was particularly interested in the position of man in nature, which made models and analogies from biology more important for his philosophy than those from physics. In order to make scientific experience possible in the first place, Kant uses “expediency” as a principle of order and structure. Similar to Aristotle, Kant defines expediency as the inner principle of living beings themselves, not as a constitutive element of nature. Only with this tool does judgment create an order principle in biology. In this way, Kant himself includes biological analogies and models in his philosophy. Not least because of this, he had a great influence on contemporary biology.

But the problem of the demarcation between animate and inanimate nature continued to be hotly debated. A "life force" should be the actual driving force of the higher development of the species. At the turn of the 20th century, the approaches of Hans Driesch ( Entelechie ), Henri Bergson ( Élan vital ) or Pierre Teilhard de Chardin ( Omega point ) were widespread and popular within and outside of science. The decline of these vitalistic positions was initiated less because one suddenly no longer perceived targeted processes, but because this approach was sterile for the current scientific method . So-called neovitalism was ultimately refuted by the work of Sven Hörstadius and John Runnström . For the history of the philosophy of biology, however, this episode provides an insight into how general philosophical conceptions are transformed into scientific research programs and how meaningful a clear separation between analytical propositions of the philosophy of science and empirical propositions of biology is.

After the unprecedented rise of modern physics and the end of vitalism in biology, the problem of demarcation became the question of the differences between physics and biology. Holistic and process-based approaches were discussed . Alfred North Whitehead put the (life) processes of organisms at the center of his metaphysics, whereby the elements of physics are more or less derived from it. As a result, this organism tends to have difficulties in reconstructing the elements of physics and has therefore only developed little concrete research to date. Samuel Alexander also tried to integrate cultural values ​​into his holism, whereby living beings and especially humans play a central mediating role in the "levels of existence". Richard Hönigswald , at the same time a physician and philosopher, developed in the 1920s, as part of his realistic criticism, a conception of the organic as a self-regulating system that is compatible with more modern approaches, such as evolutionary epistemology, and also shows approaches of a cultural philosophy .

But the mechanistic-naturalistic view has prevailed. Joseph Henry Woodger ( The Axiomatic Method in Biology , 1937) tried to axiomatically reconstruct biology in the sense of the logical empiricism of the physicalists of his time. However, this one attempt remained, since the hypothetical-deductive reconstruction is only poorly applicable to the disciplines of biology or is rejected entirely. The interest of philosophy at that time was concentrated in physics and psychology. Two developments in the middle of the 20th century, the formulation of the synthetic theory of evolution and the developments in molecular biology , then also helped the philosophy of biology to gain momentum. Since the 1970s at the latest, it has established itself as a widely ramified and serious sub-discipline of philosophy, and biological questions are among the most important in philosophy today.

Analytical philosophy of science

Ontology and epistemology

The central importance of the theory of evolution for modern biology has often been established. Under their influence, inanimate and especially animate nature are viewed as something changeable. Compared to the essentialist concepts that dominated Western thought for centuries, this is a radical change. While in Plato the timeless “idea” was the real and the concrete forms derived from it, in the context of biological evolution the concrete, temporal and changeable objects are the real.

The number of object classes considered is, however, much higher in biology than in the natural sciences of physics and chemistry . While physics only knows a few dozen object classes such as stars, planets and atoms, there are hundreds in the various sub-disciplines of biology - such as organs, cells and species. In addition, they usually have characteristic properties such as heterogeneity, complexity and dynamism. It is all the more difficult to determine the ontological and biological status of the individual object classes. The question also arises as to what the elementary objects are in the sense of a scientific approach. For example, with Rudolf Virchow the cell was the “elementary organism” and since the second half of the 20th century the focus has been on the genome . The extremely influential formulation of an ontological dualism by René Descartes subsequently enabled a methodological separation into a material and a spiritual world. In this tradition, physics experienced an unparalleled boom and the philosophy of science based on it is based on a materialistic and naturalistic understanding of nature. However, the understanding of the theory of science that emerged from this and that still prevails today is based on so-called logical empiricism , which places ontological questions under the suspicion of fruitless speculation and therefore largely ignores them.

In the search for fundamental laws and fundamental structures, one tries to trace the properties and characteristics of all research objects back to the laws of these structures. An ontological reductionism , i.e. a materialistic monism , is generally accepted today. When considering many biological phenomena, however, a reduction in theories reaches its limits, since in various fields of biology such as sociobiology or neurobiology non-material phenomena such as perception , consciousness and the will are also addressed. There are several approaches, but no convincing solution for the description and explanation of intentional and phenomenal states. The aim of many considerations is a physicalism that does not imply reductionism, since otherwise no independent biological theories would be possible. A radical mechanistic physicalism (“everything is physics”), on the other hand, would not only make it impossible to distinguish biology from physics. For some philosophers, such a physicalism is untenable if only because it would deny the difference between life and death. It is similar with the obvious difference between inanimate and animate nature. This contradiction was defused by the fact that the predominant organism model in biology switched from the machine model to the program model. The emerging cybernetics and, not least, the discovery of the genetic code brought functionalist information models to the fore. From this point of view, the highly complex organism can only function as a whole. The coexistence of mental and material phenomena is discussed today primarily on the basis of positions on emergence theory or the concept of self-organization .

Methodology and experiment

The research methods used in the biological sub-disciplines are just as extensive as the object classes examined. They range from engineering methods in biotechnology, narrative methods in neurosciences and influences from historical sciences in paleontology to bioethical issues. Explanatory theories in the disciplines of biology tend to have the character of general rules with various exceptions and only rarely the validity claim of universal laws, such as those formulated in physics, for example. Important quality criteria for scientific theories such as explanatory value, predictability and repeatability are limited in biology.

reduction

An important question is whether theories in biology can be reduced to physical (and chemical) theories. The classic approach of reducing theories by Ernest Nagel (1961) goes too far for most philosophers, since fundamental concepts such as “life” cannot be reduced. Most of the time, no need for additional physicochemical theories to explain and support life science claims is identified. For example, on the basis of the gene definition, Philip Kitcher denies that the concept of genes in classical genetics can be traced back to the concept of genes in molecular biology and gives three reasons in particular: 1. Classical genetics and molecular genetics do not correspond to the conception of theories used by Nagel. 2. The term “gene” from classical genetics cannot be described in biochemical terms. 3. Any derivation of a theory would be non-explanatory. Reductionists, on the other hand, argue that the task of deriving all biological theories from physico-chemical is today only a practical, but not a problem of principle.

In contrast, a “constitutive reduction”, that is, an adoption of theories and concepts about the material composition of organic and inorganic things, is generally accepted in biology and philosophy. Furthermore, theories in biology are usually formulated in a probabilistic way and do not describe a strict determinism as in classical physics or chemistry. But it cannot be overlooked that probabilistic theories can be strictly reductionistic, as Mendel's hereditary theory shows. Both this, which is a cornerstone of synthesis, and the synthetic theory of evolution must be classified as reductionist as long as the latter adhered to a strict gene centrism in the second half of the 20th century, which largely resulted in the evolutionary occurrences of genetic mutation randomly on the chain of arguments - natural selection and adaptation in the population. It is only slowly that today's theory of evolution succeeds in freeing itself from narrow views of this kind. Today's theory of evolution deals with far more evolutionary factors than synthesis and sees evolution more and more in interdependent contexts. This opening gives space for complex theoretical methods. This is justified, among other things, by the fact that the living systems themselves and the relationships between them, processes of nature, are highly complex, open and individual. Biological theories are usually formulated with an openness to exceptions and only claim a limited scope of application and validity. On the other hand, there are other groups who have started to explain the more complex scenario with modern methods on the basis of expanded suggestions for the framework conditions of evolution with the addition of development mechanisms ( Evo-Devo ), environmental influences, multilevel selection , niche construction and large system transitions.

Method critique

All characteristics of the living, i.e. the object of investigation in biology, also apply to the observer. Therefore, all questions in biology can be approached from the anthropomorphic internal or the technomorphic external perspective. The scope of a statement also depends on the choice of perspective. In a broader sense, all biological research is linked to historical, social, economic, political and anthropological conditions. In a contextualistic approach, methods and knowledge of biology are assessed from these perspectives. Methodological demands are also a consequence of the desire for control, manipulation and forecasting.

The positivist logical empiricism concentrates on theories and models, observations and illustrations, however, have little value. However, these methods are particularly important in biology. From the hand-drawn illustrations by Ernst Haeckel to the current imaging processes in neurosciences, the role of representation in biology is always an important and sometimes controversial topic of philosophical reflection.

Experiment and experimental systems

Although the experiment was of central importance in biological research, it was long a shadowy existence in epistemological analysis. It has been shown that, contrary to the usual view that experiments test existing theories, most and most fruitful experiments themselves have a research function (so-called exploratory experiments ). Particularly in the context of biological research, the experiment presents itself as an artificial, manipulative intervention in natural occurrences. In doing so, nature is reduced, separated and, as a rule, "conveyed through equipment". For example, vital observations (observations on living structures) are technically not possible with the electron microscope. possible. An idealized control situation in a biological experiment is not always possible. This is particularly true in ecology and behavioral research, but also in molecular biology.

Other special boundary conditions of biological research subjects such as the uniqueness of living beings, the historicity of evolution as a whole or the necessity of special environmental conditions for model organisms also cause special circumstances and limitations of biological experimental systems. The same applies to experiments on dead objects (in vitro experiments) as they are common in various sub-areas of biology. They raise the question to what extent they allow conclusions to be drawn about living systems, but also whether experimental biology is actually concerned with living nature.

Basic problems of biophilosophy

The most important topics in the philosophy of biology can be roughly divided into three areas. The central role is played by the analysis of the theory of evolution, its foundations, statements and consequences. What are species, how can they be scientifically defined, and how can they be classified and ordered. A second group of topics revolves around reduction or the relationship between physics (and chemistry) and biology. There are many technical and analytical questions that flow smoothly into the third problem group: attempts to describe what is special about living beings in nature and to attach them to criteria.

What is life

In scientific biology today, life is defined as a system of properties. Georg Toepfer lists two dozen historical - and at least six that have been in use since 1980 - definitions that all differ more or less. The terms life and living beings are not biological, but ontological terms. For the research interests and questions of biology, both terms are also irrelevant, if one wants to explicitly refer to them, one speaks of "living systems" today.

The discovery of entropy in the mid-19th century led to the widespread belief for over a century that the order of living things can ultimately not be described and explained with the aid of physics. In 1951, the physicist Erwin Schrödinger described the concept of so-called "negative entropy", today also called negentropy . According to this, living beings “feed” themselves on negative entropy; when energy is continuously supplied, living things maintain their state far removed from thermodynamic equilibrium. The ideas were later worked out through the work of Ilya Prigogine , Isabelle Stengers and Manfred Eigen to such an extent that entropy and life no longer represent a conceptual opposition today and the principle of the order of life is understood on a very general level. Due to more recent knowledge about the role of viruses and virus-like RNA groups in the evolution of life and in the regulation of almost all cellular processes, additional phenomena come into view in addition to physical conditions. This includes group behavior, cooperation and coordination, the production of completely new genetic sequences and their integration into existing host genomes.

Status and structure of the theory of evolution

Meaning of the theory of evolution

Today's synthetic theory of evolution differs greatly from the well-known, mathematically formulated theories from physics and chemistry. The attempt to formulate it according to a logical empiricism also involves some difficulties. If “natural selection” is identified as a fundamental axiom, it is difficult to derive the concept of “ fitness ” from it, since on the one hand a general law cannot be recognized, but on the other hand a relative definition is trivial. Nevertheless, fitness is the most important parameter in mathematically modeled population biology. The current status in the philosophy of biology on this problem is that greater fitness merely increases the disposition to produce viable offspring. If one continues to consider the multitude of sub-areas of the theory of evolution, such as paleontology , comparative anatomy or biogeography , and the immense number of different findings and terms, then it becomes clear that an axiomatic (re) construction in the sense of logical empiricism is not for the theory of evolution is possible. In this respect, the epistemological status of the theory of evolution in the philosophy of biology remains unclear.

The value of a scientific theory can be expressed using several criteria. First of all, one can differentiate between practical and theoretical value. The practical value of a theory consists on the one hand in the possibility of making predictions. It is generally assumed that the theory of evolution does not or hardly allows predictions. Reasons for this are the randomness of the events with regard to their meaning, the uniqueness of the individuals involved, the complexity of the systems under consideration and the occurrence of so-called emergence - i.e. known systems spontaneously develop new and unpredictable properties.

The benefits of the theory of evolution are also presented differently. The practical use of a scientific theory can be divided into the ability to make predictions and its technical applicability. The Darwinian theory of evolution is now in doubt that it allows correct predictions. However, this is countered by the fact that at least retrodictions , i.e. explanations of past developments, are possible and, in limited individual cases, even correct predictions have been derived. However, the intellectual benefit of the theory of evolution is rather emphasized. The theory of evolution does not make general statements . Due to the multitude of possible evolution factors and their random character, Darwin's theory of evolution is also not a deterministic theory. Nor is there a single canonical form of evolutionary theory to which all biologists refer equally. The importance of the theory of evolution lies above all in its role for the modern scientific worldview.

Challenge Evo-Devo

The evolutionary developmental biology (evo-devo) has taken up several issues of the synthetic theory of evolution and made clear. First of all, the concept of natural selection focuses on adult organisms and their genetic makeup. These two components - adult individuals and genes - are supposed to explain every evolutionary change in interaction with natural selection and adaptation.

But in individual development genes lead to the expression of a characteristic of the phenotype only under certain conditions or they are no more than initiation factors for the phenotypic change without being able to adequately represent it. All "intermediary" conditions are assumed. Furthermore, in most multicellular organisms all cells have the same genes, but they can develop completely differently. Classical heredity cannot explain the inheritance of developmental factors. It seems that gene expression and its conditions for evolution are more important than the genes themselves. Evo-Devo also recognizes the autonomy of cells and cell structures that enable self-organization. In such an environment, minor genetic or environmental impulses can help the system development with the help of threshold value effects and by means of its high integration ability to greater variations. In the words of Gerd B. Müller : Small disturbances (mutations, environmental factors) can show large but integrated effects (variation) on a higher level (embryonic development). The consideration of individual development leads to rejecting the gene as a fundamental unit of information and evolution. Evolution is understood within Evo-Devo as the variation and replication of entire life cycles. The genes are just one element of many.

Manfred Laubichler analyzes the methodological and epistemological differences between evolutionary biology and developmental biology and, in addition to different standards of evidence and research methodologies, also finds different ideas about causality. Evolutionary biology looks for ultimate causes, i.e. for the advantages of adaptations and the plausibility of selections, while developmental biology pursues immediate proximate causes that show up in ontogeny .

The claim of Evo-Devo in the theory of evolution goes even further: The synthesis is seen in its population-theoretical form as rather "statistically descriptive", while with the knowledge of evolutionary development mechanisms a more and more "causal mechanistic argumentation" takes hold.

The overall importance of evolutionary developmental biology is controversially discussed in the philosophy of biology and in evolutionary biology itself. The positions range from rejection of the dominance of the synthetic theory of evolution, the search for a theory extension or addition to its replacement by a "development-based" theory of evolution. It is only clear that a purely static, gene-centered approach to explaining evolution cannot be reconciled with developmental biology.

The unity of selection

The founders of the theory of evolution, Charles Darwin and Alfred Russel Wallace , disagreed on the question of where natural selection applies. While Darwin saw the individual as the only unit of selection, Wallace argued that selection also takes place at the group level. After that, group selection in biology was considered possible for almost 100 years , with the development of molecular genetics in the 1960s, new arguments were added. Since only the individual develops directly from the genes, this was not only taken as an argument for the selection of the individual organism, but the genes themselves were suggested as the level of selection. As a result, the topic was one of the most important in the philosophy of biology and was widely discussed. It turned out that “gene selection” could not adequately explain many examples in nature. In particular, it fails to explain systematic fluctuations in the frequency of genotypes. Likewise, there would have to be a clear causal chain between genotype and phenotype so that reproductive success has a direct effect on the genes. In 1988, Elisabeth Anne Lloyd proposed that the criteria for possible selection units be more precisely defined. Accordingly, a unit must interact directly with its environment. Most scientists then came to the conclusion that gene selection was untenable.

At the beginning of the twentieth century, the question of whether there is altruistic behavior between unrelated individuals in the animal kingdom and how its existence could be explained using the theory of evolution was increasingly discussed in evolutionary biology. Darwin himself brought so-called group selection into play, but his classical teaching of natural selection only knows the individual as a reproductive unit. With the development of molecular genetics in the 1960s, genes were also identified as the units of selection . As suggested by George C. Williams in 1966, genes “use” chromosomes , cell structures, and the entire organism for successful reproduction. The individual is thus only the external appearance, the real subjects of selection are the genes. Only from then on did a systematic preoccupation with this question in bio-philosophy begin. So put Stephen J. Gould (1980) and Robert Brandom determined (1984) that genes are not "visible" to the outside and are "covered" by the organism quasi. David Hull (1981) first wanted to clarify whether the carrier units of the selection can only be thought of as replicators or whether they must interact causally with their environment for reproductive success. In the second case, genes would hardly come into question as carriers.

Elliott Sober used the example of dominant recessive inheritance to show that genes cannot be causally involved in natural selection. In return, he puts forward the theory of a pluralistic and hierarchical view of selection, which is the predominant one to this day. Accordingly, there are several "levels of selection" and interaction with the environment takes place on different levels. However, there is still controversial discussion as to how these “levels of selection” influence one another and whether they can be at least partially reduced to one another. (Sober, 2003). With the advent of evolutionary developmental biology , the notion that the visible appearances of organisms ( phenotype , manifest traits ) are not only the product of genes, but also develop from the interaction of DNA, other molecules and cell structures, as well as environmental influences .

classification

The question of the ontological and epistemological status of species is often discussed in the philosophy of biology. The idea that there are clearly separate species is usually assumed unquestioned in biology. On closer inspection, however, all attempts at a clear separation are associated with various difficulties. First one has to clarify whether species or all taxa can be regarded as a mathematical or geometric class . Consequences of this would be, among other things, that the objects must have abstract, unique properties and that classes are defined via their objects. The notion of static classes, however, contradicts the evolutionary idea of ​​mutable species. With the concept of family resemblance , Ludwig Wittgenstein, on the other hand, formulated a possibility of how one can also classify through fuzzy - and thus more realistic - property definitions.

Ernst Mayr defined species as an accumulation of populations or reproductive communities. A biological species is therefore the sum of its specific variants and not an “ideal type” or mean. Instead of descriptive features, the concept of the conditions of origin and existence serves to differentiate. However, this definition comes up against its limits if, for example, one considers living beings that reproduce asexually, or if one wants to classify extinct organisms. Mayr's definition of species as reproductive communities was nevertheless a great success and largely prevailed in biology. Equally important in evolutionary biology is a classification of species based on their parentage (see phylogenesis ). Today, in biological practice, the determination of species on the basis of morphological properties is supplemented by the consideration of their ancestry history (represented by homologous genes and DNA sequences).

In 1974 the biologist Michael Ghiselin surprised everyone with the proposal to replace the abstract, essentialist and mathematical class concept with a spatiotemporal individual. Species should therefore be viewed more like organisms with an individual life cycle and concrete relationships in terms of their origin and community. The disadvantage of this concept, however, is that the use of mathematical and especially numerical methods to determine the species (“numerical taxonomy”) is dubious from this point of view. In addition, it is impossible for species to reappear after extinction. The debate about the use of concepts and criteria for classification is often conducted under the terms “species definition” and “species problem” with changing focuses and continues to this day.

Organism models and model organisms

For Aristotle, living beings, like everything else, are determined by matter and form. The “form of organisms” is the division into organs. The form and nature of the organisms correspond to the soul, whereby the difference between the animate and the inanimate is determined by the animated and the non-animated. The soul uses the body like a tool. This functional tool analogy relates to both individual organs and the body as a whole.

René Descartes made a radical change in the 17th century when he attributed the power of active activity to matter itself . Opposite it he placed the human, thinking spirit; the concept of the soul as a formative, active principle disappeared almost completely. For Descartes, life becomes the automatism of the material and the machine analogy the predominant model of the organism. Since then, organism models in biological sciences have generally been dominated by technomorphic metaphors. Current attempts to expand the machine analogy to a machine theory have not caught on because living beings break all machine metaphors with their capabilities. In order to express the homogeneity, regularity, self-similarity and order of living beings, the crystal model also became popular in the 19th century as part of the cell theory by Theodor Schwann and Matthias Jacob Schleiden . In contrast to the machine model, it does not evoke an idea of ​​planned, teleological action, since it points to an inorganic context. Theodor Schwann used the crystal analogy for cell formation, but was always aware of the limitations of the model. In this compilation one must not forget that the term "organism" is itself a "organism term". It was introduced at the beginning of the 18th century by Georg Ernst Stahl in an effort to again point out the special position of the living in an increasingly mechanized world.

In order to describe organisms and populations in today's scientific theories, biology needs formalized models. Based on a scientific model, organisms are described as physical-chemical systems. However, since neither physics nor chemistry depict the vitality of organisms, a purely mechanistic approach is considered untenable. Another approach to modeling can be found in the so-called construction morphology . Organisms are seen as mechanical energy converters. In addition to physiological aspects, the structure and shape of the organisms, especially how they work, are described using analogies to hydraulics. Construction morphological models have proven themselves more often in research practice.

With Erwin Schrödinger's book “ What is life? ”( “ What is life? ” , 1944) the idea of information found its way into biology. The carrier of this information is therefore the genetic code. Since then, analogies from computer and information technology have predominated. Examples are translation , transcription and the concept of “genetic information” itself.

Just as organism models provide starting points for questions and theories in biological research, model organisms are central to experimental research. The hope is to find general statements about functions, species or even life itself on the basis of a very limited selection of research objects. The extent to which such an extrapolation is justified is controversial depending on the individual case. The use of a certain model organism always reflects the research situation. So it would not have been possible for Gregor Mendel to derive his inheritance rules experimentally with horses, turtles or many other species. The same applies to the fruit fly Drosophila melanogaster and its importance for genetics and, more recently, for developmental biology. As part of experimental systems, model organisms in research laboratories have other special features. Efforts must always be made to establish and maintain the living conditions of the organisms. The experimental situation is inevitably controlled and manipulated.

Functions and Teleology

In addition to the question of how , in biology there is always an interest in the question of why . For example, one can ask how a human thumb works, but also why it exists at all and what purpose it serves. Convincing function ascriptions explain not only the function, but also the existence of the function holder himself. While either finalistic (related to a goal or purpose), extra-worldly forces or an immanent goal-directedness speculatively answer the questions about the purpose, the questions about the concrete function could organs and other things can be answered better with advancing experimental technology. At the same time, it remains insurmountably difficult to explain functions of phenotypic traits that might serve a purpose in the past that no longer exists today. Still, the feature is there. With the development of the theory of evolution, and in particular with the theory of natural selection, it was hoped that questions of purpose could be explained using a mechanistic and naturalistic approach. The concept of teleonomy was introduced into the philosophical discussion in order to explain adaptations as causal, coherent consequences of natural selection. The goal-oriented, shaping principle is part of a biological program. Ultimately, expediency always depends on the preservation of the species or the individual. With the help of natural selection, this then becomes part of the biological program.

However, these explanations have to face multiple criticism. On the one hand, this definition is accused of being circular because it ignores the possibility that there can also be programs that are not targeted. On the other hand, selection is only directed towards the past, it does not "plan" for the future. Carl Gustav Hempel stated in 1965 that the functional effect of a feature is always selected for the future. This separates historical evolution from functions. Furthermore, it was stated that selection theoretic approaches cannot be responsible for a purpose, since - even only hypothetically - unselected things can fulfill the same purposes. On the other hand, there could also be properties of an organism such as organ deficiencies that are not referred to as functions, but are nevertheless genetically fixed.

Teleonomic explanations in no way deny the usefulness of things, but represent them as a result of natural processes. So as long as the term teleology is used only descriptively, there is no reason for some philosophers to use another. Thus, despite all criticism, a teleological language and teleological methods are still part of biology. In paleontology in particular, there are many examples where heuristic teleological approaches are of great importance in research. The only valid form of teleology in biology is an intentionalist interpretation as a merely symbolic representation of a purpose and thus the cause of an action.

Gene definition

Molecular Biology versus Genetics

The term gene is defined completely differently for molecular biology on the one hand and for classical genetics, biological evolution theory and population genetics on the other. In the context of classical genetics , the term gene serves as a formal unit, with the help of which changes in characteristics can be generally mapped in subsequent generations. Furthermore, the separation into germline and "body substance" by August Weismann and the conceptual separation between genotype and phenotype was essential for the ideas about genes . In molecular biology, on the other hand, genes are viewed as a physico-chemical substance as part of deoxyribonucleic acid (DNA), which is also the carrier unit for “genetic information” . This made both the stability and variability of the genes and their ability to reproduce plausible. This range of possible fragmentary determination of the gene still allows a large number of definitions in the respective biological sub-disciplines, depending on the experimental system used. In biophysics , biochemistry , molecular genetics , evolutionary biology , and developmental genetics , there are different, but not inconsistent definitions.

The incentive to find a cross- disciplinary and general definition for a gene has never been very great. Today we can distinguish between two approaches. One tries to understand the gene as part of the DNA based on static, spatial and structural conditions, the other approach determines a gene with the help of the functionality of the results (e.g. proteins) as an inheritance unit or functional unit. However, it appears that more recent findings with other model organisms make further simplification and consensus-finding rather improbable.

Genetic information, genetic program

For Godfrey-Smith (2000b, 2003) the concept of genetic information is justified by the role of genes in ontogeny. On the other hand, for other authors, philosophers and biologists they are merely metaphors without any theoretical contribution to be taken seriously. According to this, the image of genetic information cannot be understood in the sense of a mathematical information theory. Two sequences of base pairs in DNA can have the same mathematical information content, but differ considerably in their “genetic information”. The quantity and coding are considered, but the meaning and function of the genetic information are consistently hidden.

Influences of biological theories on philosophy

Since Aristotle, insights, methods and theories from the doctrine of living beings have found their way into philosophy again and again. The term evolution thus conveys a central historical context for all empirical sciences (see also chemical evolution , sociocultural evolution ). The application of the theory of evolution to the question of the process of knowledge itself led to the establishment of the so-called evolutionary theory of knowledge . Then the basics of the possibility of recognition through the phylogenetic development (of humans) were created and can be described, analyzed and evaluated in this way. This interpretation touches on many philosophical topics such as the question of the recognizability of reality and the question of the quality and value of a knowledge that is completely determined in this way. According to evolutionary epistemology, evolutionary success has a direct connection with truth in the sense of a correspondence theory, as well as effects on the history of science, didactics and anthropology.

There are also attempts to apply the biological theory of evolution to ethics and aesthetics . Both approaches are very controversial, however.

literature

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Web links

Individual evidence

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