20th WCP: Biological Teleology in Contemporary Science

Attempts to reinterpret Aristotle's biological thinking in order to show its pertinence to modern biological science, as well as the attempts in the opposite direction, that is to show how hopelessly obsolete it is, are as old as biology itself. With every advancement of our understanding of living nature, there are new arguments added to these controversies. They vary by form, but basically address more or less similar philosophical questions regarding, on the one hand, our proper understanding of Aristotle's thought, and on the other, the philosophical interpretation of contemporary biological science. Today it seems that we have a better understanding than ever of both Aristotle's biological views, and of the principles and laws governing the living world. Yet the controversies about how Aristotle's ideas relate to modern biological science continue to raise some interesting and widely debated questions. From philosophical point of view, the objections that contemporary science can make against Aristotle's biology and that are encountered, in one form or another, in the literature, can be identified in three groups (without pretending to completeness). First, Aristotle's biological teleology is considered anthropomorphic in the sense that his description of nature is essentially based on the analogy with the work of a rational artist; moreover, he goes too far in this analogy, ascribing to nature cosmic goals. Second, the idea of fixed, unchangeable biological kinds is incompatible with modern evolutionary oriented biology. Third, Aristotle's final ends contradict the mechanistic spirit of modern science, which is looking only for the physical causes.

There are two ways of dealing with these objections. The first one consists in showing the many misinterpretations of Aristotle's thought that underlie some of the arguments, thus making the point that these arguments criticize Aristotle for beliefs that he had never held. The second way of dealing with the above objections explores the idea that teleological concepts are not only incorporated and widely used in contemporary science, but that in fact biology does not have to renounce teleology (as far as it is properly understood) in order to reconcile with the modern scientific method. The justification of this idea implies a philosophical interpretation of end-oriented processes in nature consistent with contemporary science.

The first line of argumentation has been mostly developed regarding the first group of objections. Several authors have shown, for example, that Aristotle's teleological views are essentially different from those of his predecessors, as well as from the theological and creationist theories with which they have been confounded by the Christian tradition. Since these questions still remain widely debated, even a simple survey of the literature dealing with them would require a much more extensive attention that it is possible here. I would like to mention, however, some recent and very interesting analyses of Aristotle's views on biological teleology and the proper way we should interpret and understand them.

One of the original moments in Aristotle's theory of biological teleology, as it has been shown by several authors, is his idea that finality resides within nature. In other words, finality is not imposed from outside upon the natural process, but is part of it (Balme, 1987). This idea distinguishes Aristotle's understanding of the final cause from the views of all his predecessors, and mainly from Plato's divine agent or Demiourgos. It is true that Aristotle distinguishes between two kinds of causes, like Plato does: causes acting by necessity and causes acting for the sake of an end, in other words, between necessity and the good or the better. For him, however, it is clear that the good', or 'the useful', or 'the valuable', is only defined from the animal's viewpoint, which means that it is not an extrinsic value-judgment. This point is crucial for understanding that in Aristotle's theory there is no any cosmic or supernatural force acting upon the living things. The sources of motion and direction, the archai or potential impulses, reside within each animal and there is nothing external to themselves that directs them. On the other hand, Aristotle's natural teleology is free of any intentionality, since in most animals there is no deliberating or purposing. It is only by nature that certain parts change for the sake of the mature organism. Therefore, the final cause does not come from an outside agent, but resides within the things that exist by nature. The direction of the individual processes is determined within the animal and the nature of animal actions must be explained only from the nature of animals. There is no overall teleological control on the processes in the living world, the only source determining their direction is the individual natures of living beings. The well known statements in which Aristotle seems to suggest that the good of some animals is subordinated to the good of others, should not be understood literally, as they only make a rhetorical account of some popular beliefs (see Balme, 275-279). Thus, finality in Aristotle's theory is directed neither by an overall controlling force operating in nature, nor by an extra factor within the individual animal, but is part of the animal's nature itself.

The question of what is the precise meaning of these natural goals, in other words, what does Aristotle exactly understand by asserting that something is, or becomes, for the sake of something, is doubtless both the most important and the most difficult one. As many authors point out, teleological explanations in Aristotle's theory are based on the idea that something happens or exists in nature because it is good from some point of view, thus linking the goal with the good, the fine, the better. The idea that the concept of a goal is the concept of something good, leads directly to Plato's influence. Aristotle himself makes the connection between 'that for the sake of which' and the good a central point to his own account of teleological description, although his understanding of the natural goals is clearly an original one (see Cooper, 1987, 245). One of the most discussed arguments that Aristotle gives for his natural teleology is the well known analogy between artistic activity and goal-directed natural processes. It seems, however, that Aristotle himself did not consider this analogy as fundamental to his theory. According to Cooper, there is another line in his argumentation that is much more important. It refers to another original idea that separates Aristotle from his predecessors, the idea that there are two distinct natures: material and formal natures. For Aristotle, the formal nature is a second level of facts and principles, which is separate from and largely independent of the material level. Explanations that refer to the formal nature are teleological in character, because they postulate as a goal the formal nature that is produced or maintained by the explained phenomenon (Cooper, 1987, 246). In other words, in Aristotle's theory, next to the material nature there is a second, distinct level of the formal nature, and it is the form of a living thing that determines the development of the foetus or the seed and subsequently the behaviour of the grown organism.

What gives the theoretical ground for justifying the appeal to goals in explaining the process of animal generation, is the fact that, for Aristotle as well as for his predecessors, it always happens in the same way. But material necessity is not sufficient to account for the production of an animal foetus, and neither is chance, since the world possesses an inherent tendency to preserve the species of living things it contains. Therefore another explanation is required. At Aristotle's time, the only alternative explanation was to introduce a supernatural power or a design operating in the living world. Aristotle's response to that was that these natural regularities are a second level of basic natural fact, a natural principle on their own. As the formal nature is another level of reality, separate and to some degree independent from the material level, so the final causality is a real causality, as real as the material-efficient one. It is located not within the material nature, but within the formal nature of a thing (see Cooper, 1987, 271-74). In other words, the form-goals of a living thing are a non-reducible part of its own nature. What is the important point here is the fact that, for Aristotle, the non-reducibility of the form-goal and accordingly of the final causality is clearly an ontological one (see also Gotthelf, 1987).

One is tempted then to declare that, in this point, Aristotle is not a modern thinker, since ontological reduction is considered as one of the fundamental achievements of contemporary science. Yet, as I have mentioned in the beginning, teleological concepts are not just widely used and incorporated in contemporary science. It could be argued that, in fact, as far as we properly understand it, teleology does not contradict the mechanistic spirit of the modern scientific method. This idea clearly emerges from the discussions on the problem of reductionism in contemporary biophilosophical literature.

The discovery of molecular mechanisms underlying biological phenomena has significantly affected the old problem of reductionism in biology. The question whether the processes characterizing living organisms can be explained completely in physico-chemical terms, was given a new strength by molecular biology. The impressive achievements of this new scientific discipline and its analytical approach were interpreted by most authors as a final argument in favour of the reductionist program. This view was defended by many philosophers and, with few exceptions, by the founders of molecular biology themselves. Discussions on reductionism were predominant in the biophilosophical literature during more than two decades, without achieving any kind of consensus on this subject. On the contrary, the problem of reductionism in philosophy of biology still remains open and extremely controversial.

There are two basic problems underlying contemporary discussions on reduction of biology to physics and chemistry. The first one refers to the fact that living beings are organized systems which show certain properties differing from those of the constituent elements. The second one, which is partly related to the first, concerns the existence of specific biological concepts and cognitive means, especially, the suitability of some biological approaches, for example the teleological language, in formulating questions and obtaining explanations. According to the reductionist program, there is no special principles of organization in living systems that cannot be reduced and expressed in terms of the theories describing the constituent elements. Moreover, teleological statements are descriptive and not explanatory, and they also can be translated into non-teleological terms. Difficulties to accomplish this program are considered to be of technical character.

For the non-reductionists, on the contrary, physico-chemical explanations of certain phenomena can never be complete. One reason for that is the teleological organization, considered as an intrinsic characteristics of living systems. Some authors point out that the understanding of the specific organization of the elements in living systems, as well as of their mode of evolution, need a special type of questions which receive teleological explanations. Since these explanations are not appropriate in the physico-chemical sciences, they are considered as distinctive for biology, ensuring its autonomy (see Ayala, 1976; Hull, 1974; Jacobs, 1986; Rosenberg, 1985; Wuketits, 1989). Furthermore, as teleology is considered to be an intrinsic characteristics of living systems, there is an explanatory relation between the higher level of organization and the constituent parts. If physico-chemical explanations proceed from the lower to the superior levels of organization, i.e. explanations of biological phenomena by their underlying elements and processes, teleological explanations, in contrast, have the opposite direction. In fact, the organizational hierarchy of living systems is not merely a result of the properties of the constituent elements, but possess an explanatory power with respect to them. In other words, the higher levels of organization express constraints which determine some systemic requirements with regard to the lower levels. Teleological explanations take into account these top to bottom relations and are necessary for biological analyses. Their reduction or transformation into ordinary (physico-chemical) causal explanations leads to a loss of explanatory power.

These ideas, or close to them, are defended by many biophilosophers who have recourse to various examples from macro-biology to support them. In molecular biology, however, there are very few attempts in justifying the necessity of using teleological or, more generally speaking, biological explanations as different from the physico-chemical explanations and providing bigger explanatory possibilities. In fact, molecular biology is still widely considered as the biological discipline the most appropriate for reduction to physics and chemistry and for elimination of teleological language. Many biologists and biophilosophers argue that the obstacles to a full molecular explanation of some processes in the cell (such as cellular development, for example), are temporary, and that molecular biology should get rid of teleology.

One of the few authors arguing that biological approaches in teleological terms are not only useful for molecular biology, but in fact have superior explanatory power than physico-chemical approaches, is Al. Rosenberg (1985). According to him, some phenomena on molecular level can be well explained in two different ways, from both biological and physico-chemical points of view, but only the biological explanations in teleological terms take into account certain important aspects of these phenomena. To justify this idea, Rosenberg analyses the way one of the recent discoveries in molecular biology has been obtained - the discovery of the reason for the difference in the chemical structures of DNA and RNA (more precisely, the fact that DNA always contains thymine and RNA uracil). The explanation of this fact was first obtained in strictly biological way using teleological language, i.e. proceeding from the effects to the causes of the phenomenon. The same phenomenon can also be explained in purely chemical way, by describing the causal chain of chemical reactions that underlie it. These two explanations are different not only in their formal structures, but mainly in their explanatory powers. Especially, from physico-chemical point of view, the universal character of the explained phenomenon is purely accidental (chemically, both DNA and RNA molecules can contain thymine or uracil), while for the biological understanding it is essential. This universal character has precise biological reasons which are central to biological explanations. Thus, Rosenberg has shown that the development of molecular biology has given to the problem of teleology even more strength than before.

Another example showing the non-reducibility of teleology in molecular biology without a loss of explanatory power, can be found in the work of Jacques Monod, one of the founders of molecular biology. He is also considered as one of the most radical reductionists in contemporary biophilosophy, whose views have been associated with the most vigorous forms of reductionism in the philosophy of biology. One of the main ideas of Monod's biophilosophical theory is that it is possible, in principle, to obtain a full understanding of the phenomenon of life, and first of all of its most characteristic aspect - its teleological properties, in terms of the underlying molecular interactions.

The main teleological functions in unicellular organisms are based on the stereospecific properties of some proteins. More specifically, the molecular mechanisms of the regulatory functions in the cell are based on the allosteric interactions between the regulatory proteins. These mechanisms are well described and, according to Monod, they can completely explain the origin, the accomplishment, and the evolution of the teleological structures and functions which ensure the coherence of the chemical activity in the cell. Thus, the nature of teleological performances of the cell lies entirely in the chemical properties and the molecular mechanisms underlying these processes.

A more careful analysis of Monod's ideas, however, shows that in his scientific analysis of allosteric interactions he has revealed the biological specificity of these processes, which he has later neglected in his philosophical interpretation. In fact, the molecular mechanisms of allosteric interactions rest on the discriminatory properties of some proteins within the non-covalent stereospecific complexes. These properties allow the establishment of a new kind of relation of a non-chemical nature between these molecules, relation which, during the allosteric processes, gives their precise orientation. This new type of interactions is not chemically determined, in spite of the fact that it is accomplished through some very chemical interactions and can be explained by them. It is established between some macromolecules (which otherwise are chemically neutral to each other), and leads to precise physiological effects concerning the conditions of adaptation and survival of the cell. Thus, the teleological functioning of the cell cannot be considered to be an ordinary chemical process. Teleology is still an objective phenomenon which ultimately rests on the underlying stereospecific properties of the biomolecules. But the specific nature of teleological performance of the cell lies in the new type of non-chemical interaction between the macromolecules, which gives a precise orientation to the chemical interactions between these molecules. This interpretation (which has nothing to do with invoking any vitalistic principle) takes into account the biological specificity of the teleological processes in the cell, which does not allow for their reduction to ordinary chemical processes (see Spassov, 1991; 1992).

In modern biophilosophy, the problem of reductionism has been treated from two general points of view. One of them focuses on the single living organism and its morphological and functional organization, trying to specify the structural order underlying its functioning. The other one refers to the whole living world and its historical development, studying the evolution of living organization. These points of view express two types of order that biology has always tried to establish in the living world and that have been unified on the level of molecular biology, after the discovery of the molecular mechanisms of heredity. In fact, the specific organization and orientation of biological processes, defined by the genetic program, can explain both the structural and functional organization of actual living beings, and their historical formation. In this way, the specific kind of functional and morphological organization distinctive of living beings, and first of all their teleological properties, have been explained by contemporary theory of evolution as mere results of their gradual formation in the course of evolution. The theory of natural selection, made more precise and substantially transformed by the molecular theory of the genetic code, has provided a physical interpretation of the mechanisms underlying the evolution of the living organisms and the transmission of their characteristics. Thus, the molecular theory of evolution has destroyed every argument referring to intentionality or to finalism (in its traditional philosophical sense) in explaining the distinctive properties of the living beings.

For many contemporary biophilosophers, the molecular theory of the genetic code has put an end to the discussions on reductionism in evolutionary theory. Some authors, however, point out that the molecular theory of evolution has eliminated teleological approaches in evolutionary biology only in a particular sense. Teleological phenomena in living beings are explained as an outcome of the genetic program, which is itself established during the evolutionary processes. This explanation of the functional and morphological organization of living systems contradicts the concept of teleology in its "traditional" sense, i.e. the notion of design or transcendental ends. As pointed out by Wuketits, contemporary theory of evolution has put an end of teleological discussions only if teleology is meant to be or to depend upon a supranatural principle (Wuketits, 1989). Teleological language is still appropriate in contemporary biology, though in a different sense. This sense can be defined in terms of program, orientation, ends, such that a system or a process is meant to be teleological if it is oriented or structured with reference to some end, which is not temporally final, but is explanatory important (see Jacobs, 1986). In this sense, a complete understanding of the functional and structural organization of the living systems is impossible without taking into consideration their particular orientation defined by the genetic program.

These two main approaches of modern biology to explaining the living world, structuralist and evolutionalist ones, can be considered as two different research programmes (see Rieppel, 1990). As such, they are autonomous and irreducible to each other, based on independent approaches to the study of the living beings. Within the structuralist research programme, teleological phenomena cannot be reduced to certain molecular mechanisms. As the examples mentioned above show, molecular mechanisms and physico-chemical interactions alone are not sufficient for fully explaining the end-oriented biological processes. This fact suggests that a single reductionist and mechanistic approach would have limited scope of validity even on the molecular level. The reduction or translation of teleological explanations into physico-chemical, non-teleological terms, while possible, results in a loss of explanatory power. A complete understanding of complex biological phenomena can only be achieved by combining both approaches.

Accordingly, we cannot derive philosophical conclusions from some results achieved only within one of these research programmes. We should base our philosophical reasoning on both of them. It is thanks to their unification that, in contemporary biology, final causality, the argument by design and the demiourgos, have been replaced by the historical contingency. In the same way, teleological concepts have to be considered as metaphors, though very useful and perhaps unavoidable ones. Still, to the extend to which these two research programmes are independent to each other, teleological reasoning remains legitimate and necessary. Within the structuralist research programme alone, without any historical or evolutionist considerations, we cannot get rid of teleology. The organism as a whole, its functioning, and even its molecular structures, are not reducible to mere physico-chemical mechanisms. The remaining 'unsolvable residue' should be accounted for through certain metaphors such as 'genetic code' or 'information'. Of course, information is neither an external principle nor something related to intentionality. It resides within the organism, it is a non-reducible part of its nature the same way as for Aristotle the form-goals of an organism are a non-reducible part of its nature. We have a historical explanation for the way this 'genetic code' and the genetic information it contains have emerged in the evolutionary process, out of certain very mechanistic physico-chemical interactions. Aristotle did not have even the possibility for such explanation. Within the structuralist research programme, however, contemporary scientific reasoning is very close to that of Aristotle. At least we could say that, in this respect, Aristotle would find himself not too alien to us.