philosophy of biology the philosophy of science applied to biology. On a conservative view of the philosophy of science, the same principles apply throughout science. Biology supplies additional examples but does not provide any special problems or require new principles. For example, the reduction of Mendelian genetics to molecular biology exemplifies the same sort of relation as the reduction of thermodynamics to statistical mechanics, and the same general analysis of reduction applies equally to both. More radical philosophers argue that the subject matter of biology has certain unique features; hence, the philosophy of biology is itself unique. The three features of biology most often cited by those who maintain that philosophy of biology is unique are functional organization, embryological development, and the nature of selection. Organisms are functionally organized. They are capable of maintaining their overall organization in the face of fairly extensive variation in their envisonments. Organisms also undergo ontogenetic development resulting from extremely complex interactions between the genetic makeup of the organism and its successive environments. At each step, the course that an organism takes is determined by an interplay between its genetic makeup, its current state of development, and the environment it happens to confront. The complexity of these interactions produces the nature–nurture problem. Except for human artifacts, similar organization does not occur in the non-living world. The species problem is another classic issue in the philosophy of biology. Biological species have been a paradigm example of natural kinds since Aristotle. According to nearly all pre-Darwinian philosophers, species are part of the basic makeup of the universe, like gravity and gold. They were held to be as eternal, immutable, and discrete as these other examples of natural kinds. If Darwin was right, species are not eternal. They come and go, and once gone can no more reemerge than Aristotle can once again walk the streets of Athens. Nor are species immutable. A sample of lead can be transmuted into a sample of gold, but these elements as elements remain immutable in the face of such changes. However, Darwin insisted that species themselves, not merely their instances, evolved. Finally, because Darwin thought that species evolved gradually, the boundaries between species are not sharp, casting doubt on the essentialist doctrines so common in his day. In short, if species evolve, they have none of the traditional characteristics of species. Philosophers and biologists to this day are working out the consequences of this radical change in our worldview. The topic that has received the greatest attention by philosophers of biology in the recent literature is the nature of evolutionary theory, in particular selection, adaptation, fitness, and the population structure of species. In order for selection to operate, variation is necessary, successive generations must be organized genealogically, and individuals must interact differentially with their environments. In the simplest case, genes pass on their structure largely intact. In addition, they provide the information necessary to produce organisms. Certain of these organisms are better able to cope with their environments and reproduce than are other organisms. As a result, genes are perpetuated differentially through successive generations. Those characteristics that help an organism cope with its environments are termed adaptations. In a more restricted sense, only those characteristics that arose through past selective advantage count as adaptations. Just as the notion of IQ was devised as a single measure for a combination of the factors that influence our mental abilities, fitness is a measure of relative reproductive success. Claims about the tautological character of the principle of the survival of the fittest stem from the blunt assertion that fitness just is relative reproductive success, as if intelligence just is what IQ tests measure. Philosophers of biology have collaborated with biologists to analyze the notion of fitness. This literature has concentrated on the role that causation plays in selection and, hence, must play in any adequate explication of fitness. One important distinction that has emerged is between replication and differential interaction with the environment. Selection is a function of the interplay between these two processes. Because of the essential role of variation in selection, all the organisms that belong to the same species either at any one time or through time cannot possibly be essentially the same. Nor can species be treated adequately in terms of the statistical covariance of either characters or genes. The populational structure of species is crucial. For example, species that form numerous, partially isolated demes are much more likely to speciate than those that do not. One especially controversial question is whether species themselves can function in the evolutionary process rather than simply resulting from it.
Although philosophers of biology have played an increasingly important role in biology itself, they have also addressed more traditional philosophical questions, especially in connection with evolutionary epistemology and ethics. Advocates of evolutionary epistemology argue that knowledge can be understood in terms of the adaptive character of accurate knowledge. Those organisms that hold false beliefs about their environment, including other organisms, are less likely to reproduce themselves than those with more accurate beliefs. To the extent that this argument has any force at all, it applies only to humansized entities and events. One common response to evolutionary epistemology is that sometimes people who hold manifestly false beliefs flourish at the expense of those who hold more realistic views of the world in which we live. On another version of evolutionary epistemology, knowledge acquisition is viewed as just one more instance of a selection process. The issue is not to justify our beliefs but to understand how they are generated and proliferated. Advocates of evolutionary ethics attempt to justify certain ethical principles in terms of their survival value. Any behavior that increases the likelihood of survival and reproduction is ‘good,’ and anything that detracts from these ends is ‘bad.’ The main objection to evolutionary ethics is that it violates the is–ought distinction. According to most ethical systems, we are asked to sacrifice ourselves for the good of others. If these others were limited to our biological relatives, then the biological notion of inclusive fitness might be adequate to account for such altruistic behavior, but the scope of ethical systems extends past one’s biological relatives. Advocates of evolutionary ethics are hard pressed to explain the full range of behavior that is traditionally considered as virtuous. Either biological evolution cannot provide an adequate justification for ethical behavior or else ethical systems must be drastically reduced in their scope. See also DARWINISM, ESSENTIALISM , MECH- ANISTIC EXPLANATIONS , MENDEL , PHILOSO – PHY OF SCIENC. D.L.H.