BIOLOGY, II (CURRENT STATUS)

This essay intends to address the status of biology as science today, and how biology relates to philosophy and to the other natural sciences.

Biology, like the other natural sciences, initially had close ties with natural philosophy. aristotle, the father of biology, saw his biological investigations in continuity with his studies of the soul and of the psychic faculties of sensation and memory. Many later biologists of note, such as Galen and Harvey, were very much influenced by Aristotle's natural philosophy, e.g., by the doctrine of the four causes, and of the special importance of the final cause.

The doctrine of "vitalism" illustrates in another fashion the close ties originally present between philosophy and biology. Although vitalism is in fact a misinterpretation of Aristotle, it was one that influenced biology for a significant portion of its history. The vitalists shared in common with the Aristotle the view that living things and nonliving things differ in kind, and not simply in complexity. The vitalists and Aristotle parted ways when it came to explaining the reason for this difference. There are a variety of vitalist positions, but they are all variations on the basic idea that living things differ from nonliving things in that living things are composed of constituents or forces that cannot be produced or cannot be active outside of the living thing. In this context some vitalists made reference to known substances, whereas others called upon some as yet unidentified vital fluid or principle. As the chemists gradually found ways of synthesizing the various known substances supposedly unique to living things, and as no additional unique motive substance or force was ever come across, the notion of a special life material or life force eventually died out.

Aristotle did not regard the difference between living and nonliving to lie chiefly in their material constituents, but in the formal principle which unifies the material constituents so that they form a whole and act as a whole. For Aristotle, every individual natural thing has a substantial form. The soul is simply a higher type of substantial form that is present in certain natural things giving them the capacity for self-motion. The soul is not some added physical substance or force. It is true that Aristotle talks about "pneuma," a physical substance primarily responsible for movement in living things, and one which is not found in nonliving things (Movement of Animals 703a4–27). Thus, the later thinkers who attempted to distinguish living from nonliving in terms of some vital fluid or vital force may well have derived this notion from reading Aristotle. It is also the case that Aristotle not only maintained that the soul is the substantial form of the body, but also held that it played an active role in controlling physical forces responsible for the processes of development and growth. Some biologists pondered how this might be and tried to incorporate this notion in their scientific explanations (e.g., Hans Driesh [1867–1941]), but the eventual trend was to leave such problems to the philosophers, and to look to chemistry and physics to unveil the immediate causes responsible for specific motions within the body. The growing success in the latter enterprise in stark contrast to the difficulty of the philosophical issues regarding body-soul relations were in part responsible for the eventual dichotomy between philosophical and biological inquiry regarding living things.

The other major factor that led to the present-day division of biology from philosophy was a change in the methodology which gained impetus starting with the Renaissance. The gradual development of the hypotheticodeductive method as the method of science marked a significant break between natural philosophy and the natural sciences. This method first gained widespread usage in physics. The hypothetico-deductive method starts from a question raised by the observation of facts. The next step is to interrelate and generalize the facts in the form of laws. A hypothetical cause is then posited for why the laws obtain, and then deductions are made in light of the supposed cause of other phenomena which should occur. These deductions are then tested through observations that are most often made in the context of experiment. The logic of the situation is such that while incorrect predictions establish that one's hypothesis is mistaken, correct predictions can never prove, but can only corroborate one's hypothesis. Hypotheses are thus always subject to being revised in light of new facts. Since proceeding by hypotheses and experiments is very different from proceeding by formulating definitions, making divisions, and using dialectic, the growing use of the scientific method widened the gap between biologist and philosopher.

While biology in some sense emancipated itself from philosophy by adopting the scientific method, by the same token it now had to establish itself as a genuine science alongside physics and chemistry. The fact that the scientific method was first used to any great extent in physics put a certain slant on what came to be regarded as the criteria for what was scientific and what was not, criteria that biology did not always meet. These criteria are as follows. First, control is crucial when performing experiments. It is needed in order to achieve precision, for one can only isolate a specific aspect of a phenomenon by holding the other aspects constant. Control is also needed in order for an experiment to be repeatable. If a scientist does not define the precise parameters under which the experiment is performed, other scientists cannot check the accuracy of the results. Second, experimental results are to be obtained through measurement (reflecting again a concern for precision), and scientific generalizations are to be arrived at by formulating experimental results into laws of a mathematical character. Experimental results and laws are to be expressed in unambiguous terms, namely, in terms of numbers and symbols. Third, in science complex wholes are regarded as fully explicable through an analysis of their parts.

Biology for some time was regarded as "soft" science because it does not completely meet the criteria elaborated in physics. This, however, is not to biology's discredit. After all, there are important differences between the things studied in the two areas. Living things in contrast to nonliving things are characterized by variety, variability, and manifest orientation to goals. There is a much wider variety of species than of atomic particles and chemical elements, and individuals within a species differ more from one another than do samples of chemicals of the same type. Living things develop through time (they have life cycles), and new species have developed in the course of the history of our planet. Organisms pursue recognizable goals, and have organs by which they do so. Moreover, they are only adequately understood in relation to other living things and to the environment.

Biologists are capable of performing experiments under controlled conditions, granted that in areas such as animal behavior the ability to exercise control is not as great as in those areas where biochemistry plays a greater role. Claude Bernard's work An Introduction to the Study of Experimental Medicine (1865) is noteworthy for explicitly addressing how the experimental method is to be applied in biology so that the control and repeatability that is the hallmark of science can be obtained.

As for the role of measurement and mathematical formulas, biology does not meet the physicists' expectations. Experimental results in biology are not always precise, and thus they cannot always be expressed in rigorous mathematical terms. The weight of an individual cow is not a constant as is the weight of a chemical element. Moreover, many important facts about living things cannot be expressed mathematically, including the behavior of an organism as a whole, the function of organs, and the relation of an organism to other organisms in its environment. And this affects the formulation of biological laws. Regularities between phenomena certainly have been discovered in biology, e.g., growth is stunted in poorly nourished children. However, regularities of this sort are often not called laws either due to their relatively narrow scope, or because they are not precise and mathematical, or because they admit of many exceptions, or a combination of these factors. For example, the flowering of different species of plants is stimulated by different external conditions and internal factors (such as hormones), and so the description of what happens in one species may vary considerably from what happens in another. There are no ideal laws of plant blooming, as there are ideal gas laws (though one may question how well the ideal gas laws apply to reality). Biology is not to be faulted in such cases because it cannot be more precise and cannot give exact formulae. To be more precise would result in inaccuracy rather than science. Accordingly, in biology books one find more models than equations (genetics being a partial exception), and more descriptions than symbolic representations.

To a large extent biology has adopted the reductionist approach of physics and chemistry whereby complex wholes and their activities are understood by understanding the workings of their constituent parts. The reductionist approach of explaining life processes in terms of the molecular constituents upon which they depend has proven itself to be a very powerful approach. Some biologists consider the philosophical question that naturally arises as to whether such reductionism is merely methodological or whether it is ontological, i.e., whether living things can be fully understood in terms of their material parts and their interactions. The debate becomes especially acute when it comes to determining how to explain phenomena such as consciousness. What is sometimes over-looked is that the reductionist approach is not the only approach that is currently used in biology. Another approach that is used is historical. It attempts to explain the parts and behavior of organisms in terms of their evolutionary ancestry, as in, for instance, the explanation of the presence of vestigial organs. Biology also sometimes proceeds in a way similar to natural philosophy, taking rather common observations as starting points, and trying to give some explanation of these well-known phenomena in terms of causes, especially in terms of the final cause. For example, biologists inquire why some trees lose their leaves in autumn. This sort of question is not answered in terms of material constituents, but in terms of what the part or process contributes to the well-being of the individual organism or to its reproductive success.

The practical applications of biology are what define it against physics and chemistry in the minds of many biologists. Physics sends people to the moon, whereas biology cures diseases and genetically alters organisms. Biologists approaching the question in a theoretical manner distinguish biology from physics and chemistry to a greater or lesser degree corresponding to the type of reductionism they embrace. One widespread view is that biology differs from the other natural sciences to the extent that it deals with the unique ways in which physical and chemical reactions are organized within living systems. Another popular view maintains that there are different levels of biological organization, and that the higher levels bring with them emergent properties that are not found at the lower levels. However, there are many other views as well, views which could only be completely enumerated and categorized by examining in detail all the different forms of reductionism.

Biology and Philosophy. An important area of debate, especially among evolutionary biologists, regards the nature and role of teleological explanation in biology. There is a strong current among contemporary biologists and philosophers of biology to eliminate any mention of final causality, either by a type of reduction of the final cause to the efficient cause, or by redefining it in some other way and renaming it (e.g., calling it teleonomy). Certainly what constitutes a proper biological explanation is at stake. However, oftentimes there is another underlying issue, namely, the philosophical question of whether natural causes alone can explain the order found in living things. Biologists often shy away from or reject any acknowledgement that organisms manifest finality or design, because they are concerned that they will have to follow the reasoning articulated by William Paley which concludes that there is a supernatural designer. At the same time, biologists cannot help asking when they see a structure or process for the first time: What is it good for? E.g., biologists seek to determine not only how the flying fish fly, but why. The majority of evolutionary biologists who acknowledge the importance of "why?" questions, and who address the philosophical question of whence the origin of the ordering to an end found in living things, maintain that the observed finality is due to the blind forces of chance and necessity. Chance provides new variations, and necessity (commonly referred to under the name of natural selection) determines which variants are reproductively successful. This view is contested by the proponents of the Intelligent Design movement who argue that the order found in living things requires an intelligent agent outside of nature to adequately explain it.

There are other issues in evolutionary biology as well which are either essentially philosophical or which take their point of reference from philosophical discussions, e.g., the questions of what constitutes a biological species and what constitutes the proper manner of classifying organisms. In other parts of biology, as well, philosophical issues arise, such as, for instance, neuroscience questions concerning the nature of consciousness and emotion. There is one philosophical issue that comes up in biology, however, which merits special mention because of its very general scope: namely, the question of certitude. The widespread notion among biologists is that certitude can never be achieved; everything in biology is subject to revision. This skepticism arises in part from the influence of philosophers such as Descartes, Hume, and Kant. It also has roots in the claims of certain philosophers of science.

The philosopher of science Thomas Kuhn (1922–1996) promoted the view that all observation is theory-laden, i.e., that what one sees always involves interpretation in light of a theoretical framework, and thus all observation lacks objectivity. This view when taken to the extreme denies the possibility of genuine scientific progress. Consider, for example, the historical case of biologists who, using a microscope, claimed to see miniature fowl in unincubated eggs and miniature humans (the "humunculus") in human sperm. It is reasonable to think that the scientists in question made these inaccurate observations because they were influenced by the preconceived notion that the parts of the adult were already present in the germ cell and only needed to grow (the notion of "preformation"). However, when later scientists determined that these observations were inaccurate, it was not the case that it was simply a change in preconception that accounted for why they did not observe miniature parts, but it was also because there were no miniature parts to be observed. Even Charles Bonnet, an advocate of the doctrine of preformation who gives a forced explanation of why there is an observed lack of part-to-part correspondence between the early embryo and adult, nonetheless did not fail to note that under the microscope no such correspondence is observed.

The philosopher of science Karl popper (1902–1994) insisted upon the logical point that one can only falsify a hypothesis; one can never prove it. Correct deductions from a hypothesis serve to corroborate it, but not prove it, since some other hypothetical cause might account for the very same phenomena. Biology, however, unlike the other natural sciences, is sometimes capable of replacing hypotheses with observation. Dissection can reveal structures and their activities that were previously hidden. For instance, Galen refutes erroneous notions about the function of the ureters by doing experiments which involved cutting an animal open (On the Natural Faculties, bk. I, c. 13). Microscopes, from the light microscope to the electron microscope, have been a tremendous aid to the biologist by making visible structures that formerly could only be hypothesized to exist. For instance, while Harvey could only hypothesize that there existed vessels connecting arteries with veins, later on Malphighi, using a microscope, actually saw the capillaries that link the two. Facts discovered in these ways are not subject to revision (e.g., there is no doubt that the heart is an organ the function of which is to circulate blood in the body). The biologist is not so bound to formulating hypotheses as the physicist is because the objects the biologists observes are sometimes either macroscopic or at least visible with a microscope. Thus, in some cases biology attains a high degree of certitude, and one that excels that which is achieved in physics.

Biology today on the whole looks as if it were an entirely different enterprise than philosophy, especially due to the use it makes of the scientific method. However, closer examination reveals that the moment biologists begin to reflect upon methodological issues, such as whether the reductionist approach is sufficient or what constitutes a proper understanding of teleology or what kind of certitude can be achieved, they are engaging in philosophical reflections. Aside from these very general issues, philosophy is also important in certain discussions which come up in the context of particular parts of biology, questions ranging from the definition of "consciousness" to what role, if any, chance, necessity, and mind play in the evolutionary process. Certainly the tremendous advances that have been made in biology in understanding the workings of the cell and of heredity, as well as in understanding and curing various diseases—advances which make it perhaps fair to call biology the ruling science of the day—were due to the application of the scientific method, and not to philosophical discourse. At the same time, biology will always have ties with philosophy to the extent that a full understanding of the nature and origin of living things, as well as of the status of biology as science, are objects of philosophical reflection. Also not to be forgotten is the utility of moral philosophy for biologists faced as they are with difficult moral choices regarding the development of new technologies, experimentation on human and animal subjects, and other moral issues that arise while doing research.

[m. i. george]