Wednesday, April 29, 2009

The Idea of Nature, Part 2

Nature as Organism and Nature as Machine

The contrast between traditional and modern concepts of nature might be presented as a contrast between visions of nature as an organism and as a machine. For many of the Greek philosophers and medieval theologians, nature was primarily manifest as something that is born and grows. Even for premodern materialists such as Lucretius, nature seems to be a super-organism with a consequent sacred or awe-inspiring character. Although he seeks to remove all religious superstition from the world and present nature as devoid of gods, his poem De rerum natura opens with praise of sky and earth as the father and mother of all living things. In the presence of such a reality--indeed, as part of such a reality--humans are called upon to accept and to live in harmony with it. For Plotinus, throughout "the air, the earth and sea, there are advents of terrestrial, aquatic, and aerial gods so that the world is throughout filled with deity; and on this account is according to the whole of itself the image of the intelligible."

For modern philosophers such as Descartes, however, nature was primarily manifest by inanimate entities that interact as carriers of energy to create complex structures. For Descartes, even living beings are complex machines--plants, animals, and human bodies (including the human brain and nervous system) are all machines.

Such a view of nature as machine undercuts the traditional distinction between nature and artifice. The science of nature as machine yields a technology by which nature as technology can be further molded by human beings to serve human purposes. When Bacon declared that "nature to be commanded must be obeyed," he transforms the premodern basic end in itself of obedience to nature into a mere means for power over nature. Although he argues that all humans can do "is put together or put asunder natural bodies" with "the rest being done by nature working within," for him nature as a mechanical process has already ceased to exhibit much in the way of intrinsic worth.

From the nineteenth-century romantic poets to contemporary deep ecologists, humans have worried that the science and technology of nature as machine brings about first in theory and then in practice, in Bill McKibben's phrase, "the end of nature"--a wholly artificial world controlled by human will with no room left for natural spontaneity or wildness.

In response to this romantic notion of nature and technology in conflict, some people have defended technology as itself natural. All organisms alter their environments in adaptive ways, and many animals build artificial structures. Beavers construct dams, bees fabricate hives, leaf-cutter ants cultivate fungus gardens and herd aphids. Darwin contended that tool-making was common in the animal world, and human technology differed in degree but not in kind.

Some biologists today argue that human technology expresses "niche construction," which is a trait found generally in the living world, because organisms do not just adapt to fixed environments, they also change environments to construct their own niches. There is no fixed "balance of nature," because nature is constantly in flux from the ever-changing forces of both physical and organic causes. For example, the present concentration of oxygen in the atmosphere has arisen from the production of oxygen by photosynthetic organisms. As a consequence, many organisms have evolved a capacity for aerobic respiration and other traits as adaptations to this atmospheric increase in oxygen levels over the course of geological time. Without such a change in the atmosphere brought about by ancient photosynthetic organisms, human beings could never have evolved.

We often think of human culture as a uniquely human realm of artifice transcending nature. But in fact, many animals are capable of cultural learning from other animals, and this cultural learning can be passed down by behavioral inheritance, which creates a process of behavioral inheritance that goes beyond, while also interacting with, genetic inheritance. (A good survey of the evidence for this is presented by Eytan Avital and Eva Jablonka in Animals Traditions: Behavioural Inheritance in Evolution [2000].)

The Morality of Nature

Throughout history, it has been common to appeal to nature as a guide to morality through ideas of "natural right" or "natural law." But the critics of this moral conception of nature complain that this kind of thinking suffers from confusing distinct senses of nature.

Insofar as nature covers the entire order of things, argued John Stuart Mill (in his essay "Nature"), the moral injunction to "follow nature" makes no sense, because humans have no choice in the matter. Everything people do must conform to nature in this abstract, all-encompassing sense. On the other hand, if nature is the spontaneous order of things free from human influence, then "following nature" would be irrational and immoral. It would be irrational, because any human action would alter the course of nature and would thus be unnatural. And it would be immoral, because natural phenomena often have evil effects. Mill declares: "Either it is right that we should kill because nature kills; torture because nature tortures; ruin and devastate because nature does the like; or we ought not to consider at all what nature does, but what it is good to do." Surely, Mill insists, morality requires that we go against the impulses of nature.

Morality is not natural, Mill concludes, because it must be artificially perfected by human cultivation and artifice to satisfy the moral concerns of human beings. Those who argue for a natural moral law mistakenly assume that what is can be the rule and standard for what ought to be. Natural science can reveal the natural facts of existence, but morality must tell humans about the moral values of human life.

This distinction between is and ought, or between facts and values, supports the common distinction between nature and culture. Morality is assumed then to arise not from nature but from culture, because moral norms of right and wrong, good and bad, are products of human cultural artifice. Through science, people can understand nature. And through technology, people can control nature. But to judge the moral ends of scientific understanding and technological control, one must go beyond nature and enter the realm of culture, which is an artificial world of human social contrivance set apart from the natural world. As Remi Brague has shown (in The Wisdom of the World [2003]), Mill's essay on nature manifests the shift from the premodern idea that nature is a model for human action to the modern idea that nature needs to be corrected, not imitated.

As a proponent of "Darwinian natural right," I respond to this by saying that although cosmic nature might be indifferent to moral distinctions, human nature is not. If one can identify some human desires and inclinations as natural and not merely conventional, one can say that the naturally good life is one that satisfies those natural desires and inclinations to conform to some deliberate conception of a whole life well lived. So, for example, if human beings have natural desires for life, for parental care, and for social bonding, then one can judge those beliefs and practices that satisfy these desires as naturally good.

Even Mill accepts this in his utilitarian morality, when he claims that the ultimate good for human beings is the attainment of happiness, which is the fullest satisfaction of their natural desires over a whole life. For example, humans' moral duties to others arise from their natural sentiments as social animals who care for their fellow creatures. Of course, as Mill insists, people's moral values do not spring spontaneously from their inborn human nature, because they need to be cultivated through individual habituation and social customs. But still, as Aristotle said, the cultivation of such virtues is made possible by our natural desires and propensities. It is natural for us to fulfill our nature by nurturing it.

To ponder such questions about the meaning of nature expresses some of the deepest desires of our human nature.

Some of my previous posts on the is/ought question can be found here, here, and here.

Sunday, April 26, 2009

The Idea of Nature, Part 1

The English word nature is derived from the Latin word natura, which is related to the verb nasci (to be born) and the noun natus (birth). The Latin natura corresponds to the Greek phusis, of which the root is phuo (growing, becoming, being). This etymology suggests that nature is the original birth or coming into being of something. More generally, nature is concerned with "first things," the origins of things.

The idea of nature was first formulated by ancient Greek philosophers and scientists. Aristotle identified the "first philosophers" as "humans who spoke about nature" in looking for the "principles" or "beginnings" of all things.

These Greek philosophers thought of phusis as the beginning or coming to be of something. But more often phusis meant the sort or kind or description of something--the distinctive character of a thing or class of things. The nature of something could be what it is at birth, or it could be what it grows into at maturity, what it is at its beginning or at its end. "Nature is an end," Aristotle claimed, "because whatever anything is like when its growth is completed, that we call the nature of each thing." These Greek philosophers began by asking about the nature of each thing, what each thing is like. Thus, the Greek philosopher Parmenides could write a book with the title On Nature, which considered the "nature" of everything.

When nature becomes everything, it is impossible to define. But generally nature is a term of distinction, and so its meaning can be clarified by asking what is its opposite. In ancient Greece, "nature" (phusis) was most commonly set in opposition to "custom" (nomos) or "art" (techne). Custom and art are human products. By contrast, nature is what arises on its own without human interference. Nature is what is not customary or artificial. (The simple dichotomy becomes dubious, however, as I will suggest later, when we consider how natural potentialities or inclinations depend on habit, culture, or art for their completion.)

Philosophy or science arose in ancient Greece when a few thinkers noticed that customary practices and beliefs varied across human societies. This led them to doubt the authority of human customs and to look for what was universally true by nature as opposed to what was believed to be true by human custom. Whatever arises by human custom or artfulness is changeable, but what arises by nature, it was argued, is unchangeable and thus more real than the perishable products of human activity. And yet, biologists such as Aristotle could see that living beings show a natural contingency or historicity in their coming into being, growing to maturity, and passing away.

The ultimate justification for customary practices and beliefs can be the claim that they are divine, that they originated from the commands of gods or god-like ancestors. But when Greek philosophers and scientists explained the "first things" as natural rather than customary or artificial, this suggested that even the gods might be artificial or human-made, as being products of storytelling. The natural was opposed to the divine or the supernatural. Consequently, as indicated by the Athenian trial and execution of Socrates, who was charged with impiety, the philosophic discovery of nature implied a questioning of the gods.

The religious believer could respond by denying the idea of nature as the autonomous order of the world and affirming that whatever exists is what it is only through the creative activity of the gods or God. The Hebrew scriptures contain no word that corresponds to nature. In the Greek New Testament, the word phusis does not occur except in the letters of Paul, who was influenced by Greek philosophy. Nevertheless, some interpreters of the Bible have argued that it assumes the existence of a natural order of things, even if that natural order depends ultimately on God's creative will.

Among many early and medieval Christian theologians, the Greek idea of nature was adopted, but with the understanding that this nature was created by God. This allowed Thomas Aquinas, for instance, to interpret the order found in the cosmos as "eternal law" and in human nature as "natural law." The natural law of what it is to be human was manifest in three levels of natural inclination or desire: for physical life, for family and children, and for political and rational experience.

In the late medieval period, as creation itself increasingly came to be conceived in technological terms, this led to nature being thought of as God's artifice. As a divine construction, nature could stand on its own and was governed by its own "secondary laws." Although God ultimately remained the transcendent "first cause" of all things, the divine began to be pushed to the margins of scientific inquiry.

The founders of modern science such as Galileo Galilei, Francis Bacon, Robert Boyle, and Isaac Newton adopted this medieval teaching in defending the science of nature as the study of "secondary causes," as distinguished from Biblical theology as the study of God as "first cause." Nature was the book of God's works, and the Bible was the book of God's words. To understand nature, scientists must strive to understand the principles of nature that constituted the laws of nature. Charles Darwin appealed to this "two books" idea to justify his scientific study of living nature.

Some people have seen a contrast between the fundamentally theoretical understanding of nature in premodern science and the fundamentally technological understanding of nature in modern science. Premodern scientists seem more concerned with the intelligibility of nature, while modern scientists seem more concerned with the mastery of nature. Modern scientists under the banner of Bacon and Descartes seem to strive for power over nature, so that the point is not just to understand nature but to change it, and thus modern science seems to manifest an inherently technological orientation. As I will suggest, however, in some subsequent posts, I think this sharp contrast between premodern and modern science is overstated: even if modern science tends to stress the technological conquest of nature, modern science is still motivated by the same natural desire for understanding that drove premodern science.

Wednesday, April 22, 2009

Darwinism and the Catholic Church

In 1633, the Catholic Inquisition condemned Galileo as a heretic for endorsing the Copernican heliocentric theory of the Earth as moving around the Sun, because this seemed to deny those Biblical passages that spoke of the fixity of the Earth. Galileo was sentenced to house arrest, and his book Dialogue Concerning the Two Chief World Systems was put on the Church's Index of Prohibited Books.

By contrast, Darwin's theory of evolution has never been officially condemned by the Vatican, and his books were never been put on the Index, although a book by his grandfather Erasmus Darwin was put on the Index.

The Catholic Church's condemnation of Galileo has often been cited by those who argue that there must be perpetual warfare between Biblical religion and modern science. But the Church's handling of the debate over Darwinian evolution shows that the Church's hierarchy learned a lesson from the Galileo affair--that it was a big mistake to interpret the Bible as contradicting modern science.

By the middle of the twentieth century, Pope Pius XII praised Galileo as an intellectual hero and declared in his 1950 encyclical Humani Generis that there was no necessary conflict between Biblical faith and the theory of evolution. Pope John Paul II apologized for the condemnation of Galileo, and in 1996 he declared that the Church did not oppose Darwin's theory. A few years ago, I wrote a short essay on John Paul's statement.

We now have more information about the history of the Vatican's deliberations about evolution. In 1998, Cardinal Joseph Ratzinger (now Pope Benedict XVI) authorized the opening of the Archive of the Congregation for the Doctrine of the Faith in the Vatican. This congregation was originally called the Holy Roman Inquisition, which goes back to the beginnings of the Inquisition in 1231. This Archive includes the records of the Vatican's handling of the evolution debate at the end of the nineteenth century.

This archival material has become the basis for a book--Mariano Artigas, Thomas Glick, and Rafael Martinez, Negotiating Darwin: The Vatican Confronts Evolution, 1877-1902 (Johns Hopkins University Press, 2006). The book studies the cases of six Catholic authors who argued for the compatibility of evolution and Christianity. Of these, the most fascinating case, I think, is that of John Zahm, an American priest at the University of Notre Dame who provoked controversy with his book Evolution and Dogma (1896), which defended theistic evolutionism. The case of Zahm was complicated by the fact that he was identified as a proponent of "Americanism"--a movement among American Catholics to celebrate the moral and political principles of American life (such as the separation of Church and State) as a guide for Catholics.

Zahm defends the theory of evolution as superior to the theory of special creation. God did not have to miraculously create each form of life, because He could employ the "secondary causes" of evolution to carry out His creative purposes. Against the view of many Catholic theologians that God had to miraculously create the body of the first man, Zahm suggests that the human body could have originally evolved naturally from primate ancestors. But then the human soul had to be created immediately by God. To defend his position, Zahm had to argue that the Bible should not be read literally as a text of science, and that the distinction between God as Primal cause and nature's secondary causes allowed natural evolution as a creative process.

The newly available archival material shows that while Zahm's book was condemned by Church authorities, this condemnation was not published or officially sanctioned by the Holy See, and his book was not listed in the Index.

What one sees in this and the other cases is that the Vatican was cautious in not wanting to publicly condemn evolution for fear of falling into something like the Galileo affair.

Pope John Paul II's statement in 1996 shows how far the Church has moved towards accepting Darwinian evolution. In effect, as I argue in my essay on the Pope's message, he adopted St. George Jackson Mivart's position that while the human body and all other forms of life might be products of Darwinian mechanisms, the human soul must have been created directly by a miraculous intervention of God into nature.

As I indicate in my essay, the next good step for the Vatican would be to recognize that even the human soul could have arisen by a natural process of emergent evolution in which differences in degree become differences in kind after passing over a critical threshold in the size and complexity of the primate brain.

As indicated in a recent article in Scientific American, comparisons of the genomes of humans and chimpanzees suggests that the uniqueness of human beings could have arisen from some uniquely human DNA sequences that regulate the development of the human cerebral cortex and neural mechanisms that control the human capacity for speech.

If our being created in God's image is manifested in our uniquely human capacities for reason and speech, the emergent evolution of the brain to support those capacities could explain the natural basis for that creative activity.

Wednesday, April 15, 2009

Does Evolution Explain Human Nature?

Does evolution explain human nature?

That's the question posed by the John Templeton Foundation to a dozen scholars of biology--Francisco Ayala, Francis Collins, Eva Jablonka, Lynn Margulis, Geoffrey Miller, Simon Conway Morris, Martin Nowak, Joan Roughgarden, Jeffrey Schloss, Frans de Waal, David Sloan Wilson, and Robert Wright. Each wrote a brief essay in response. All of the essays can be found on the Templeton website.

These essays challenge four of the major misconceptions about evolutionary explanations of human nature. It is often said that such evolutionary reasoning (1)promotes atheism, (2) assumes genetic determinism, (3) subverts morality, and (4)denies the wondrous mysteries of life.

All of these authors accept the truth of evolutionary reasoning in explaining--either partly or entirely--the complexity of human nature. Some of them are religious believers, and two of them (Collins and Nowak) write about their Christian beliefs. Some of the others speak about the importance of explaining the evolutionary origins of religiosity.

That genetic determinism is insufficient for explaining human nature is a major theme for nine of the authors (Ayala, Collins, Jablonka, Margulis, Miller, Morris, Nowak, Schloss, and Wilson). Margulis speaks about "symbiogenesis, the evolution of new species from the coming together of members of different species," and this goes beyond random genetic mutations. Many of these authors stress the importance of cultural evolution, particularly through the human capacity for symbolism. An evolutionary explanation of human nature requires an account of the complex interaction of genetic evolution and cultural evolution.

The most interesting essay on the multi-leveled character of human evolution is Jablonka's. She suggests that an evolutionary explanation of human nature would have to reformulate Aristotle's biological psychology in an evolutionary framework. Aristotle explained human nature--particularly in the De Anima--as manifesting three levels: goal-directed living systems, animal mentality, and human thought. She argues that evolutionary explanations must move through these levels. We need to define evolution as "the set of processes that lead to changes in the nature and frequency of heritable types in populations over time." These "heritable types" include "genotypes, types of transmissible epigenetic (that is, developmentally acquired) variations, types of socially learned animal behavior, and types of symbol-based transmitted information." Jablonka's reasoning is elaborated in her book Evolution in Four Dimensions, which supports the same complex view of human evolution that I will develop in my new book.

Against the claim that a Darwinian view of human nature denies the importance of morality, six of the authors (Ayala, Collins, Jablonka, Margulis, de Waal, Wilson, Wright) emphasize the importance of morality for human evolution. Although the capacity for human morality is rooted in human genetic evolution, the development of moral experience depends on human cultural evolution.

Here is where I would say that we need to move through three levels of analysis--natural order, customary order, and deliberate judgment. The evolutionary history of human morality shows the universality of moral sentiments, the variability of moral traditions, and the individuality of moral judgments.

Many people think that evolutionary explanations of human nature gloss over the deep mysteries of the human condition. But some of these authors (especially, Collins, Nowak, and Wright) insist that evolutionary science forces us to confront the inescapable mysteries of human life. Collins writes: "We see science as the way to understand the awesome nature of God's creation and as a powerful method for answering the 'how' questions about the universe. But we also see that science is powerless to answer the fundamental 'why' questions, such as 'Why is there something instead of nothing?,''Why am I here?,' and 'Why should good and evil matter?'" Nowak speaks of "the mystery and purpose of life, which cannot be answered by natural science alone." And Wright points to two "awe-inspiring mysteries"--the mystery of the cosmic First Cause and the mystery of consciousness.

Nowak thinks another kind of mystery is manifested in mathematics: "the great theorems of mathematics are statements of an eternal truth that comes from another world, a world that seems to be entirely independent of the particular trajectory that biological evolution has taken on earth." We must wonder how "evolution has led to a human brain that can gain access to a Platonic world of forms and ideas."

The conclusion I draw from all these essays is that an evolutionary explanation of human nature requires a combination of all the traditional intellectual disciplines--in the natural sciences, the social sciences, and the humanities--as we strive for a Darwinian liberal education in pondering the deepest questions of human existence.

Sunday, April 12, 2009


A few years ago, I participated in a year-long lecture series on biotechnology at Rochester Institute of Technology. This was organized by John Murley in the Political Science Department. He brought together a broad selection of prominent and thoughtful speakers to offer a diverse range of positions on human biotechnology--ranging from leading critics of biotechnology (such as Leon Kass and Francis Fukuyama) to leading proponents (such as Ronald Bailey and Lee Silver).

Now, the State University of New York Press is publishing a book that includes some of the papers presented in that lecture series. The book is edited by Sean Sutton at RIT. The book will be available in July.

Here's the publisher's information on the book.

Biotechnology: Our Future as Human Beings and Citizens, edited by Sean Sutton.

An essential introduction to a controversial yet crucial field of research, Biotechnology surveys recent advances in the field and offers a wide range of opinions for and against expanding this new branch of science. Incisively examining such key topics as therapeutic cloning, genetic enhancement, stem cell therapy, and the use of psychotropic drugs such as Prozac and Ritalin, contributors to this volume agree that biotechnology will inevitably change human life. However, they debate the right way to balance the potential to cure disease and relieve human suffering with the need to respect human life and preserve human dignity. Several explore the way major religions--both Eastern and Western--treat the subject. Others analyze the role of government in biotechnology and specific applications of the technology that should be practiced. Serving as an introduction to this ethically complicated and significant scientific movement, the book ultimately raises the broader, fundamental question of the meaning of human flourishing.

Table of Contents

Introduction: Biotechnology, Human Being, and Citizen
Sean Sutton

1. Biotechnology and Our Human Future: Some General Reflections
Leon R. Kass

2. Who's Afraid of Posthumanity? A Look at the Growing Left/Right Alliance in Opposition to Biotechnological Progress
Ronald Bailey

3. Bioethics and Human Betterment: Have We Lost Our Ability to Dream?
Ronald M. Green

4. Biotechnology in a World of Spiritual Beliefs
Lee M. Silver

5. Jewish Philosophy, Human Dignity, and the New Genetics
Hava Tirosh-Samuelson

6. The Bible and Biotechnology
Larry Arnhart

7. A Transcendent Vision: Theology and Human Transformation
Richard Sherlock

Thursday, April 09, 2009


Darwinian Conservatism: A Disputed Question, edited by Kenneth Blanchard, is a new book published by Imprint Academic. It will be available sometime in May.

Part One of this book will be a reprint of my Darwinian Conservatism as it was originally published in 2005.

Part Two will be devoted to the following eight "critical responses" to the book:

Neil Blackstone, "Darwinian Conservatism: One Biologist's View"

Lauren Hall, "The Liberated Beast"

Carson Holloway, "Darwinian Conservatism and the First Cause of All Things"

Peter Augustine Lawler, "All Larry Needs is Love (and Death)"

Timothy Sandefur, "Darwinism and the Limitations of Conservatism"

Richard Sherlock, "Darwinism and the Limitations of Naturalism"

Michael Shermer, "Why Christians and Conservatives Should Accept Evolution"

John G. West, "The Misguided Quest for Darwinian Conservatism"

Part Three of the book contains my response to these critics and a final chapter by Blanchard:

Larry Arnhart, "Vindicating Darwinian Conservatism"

Kenneth Blanchard, "Natural Right and Natural Selection"

Blanchard's chapter offers some thoughtful reflections about how Aristotelian natural right might be compatible with Darwinian natural selection.

The whole book is about 300 pages long. It's available for preorder at Amazon.

Saturday, April 04, 2009

Aristotle, Darwin, and Marjorie Grene

Marjorie Grene, a retired professor of philosophy at Virginia Tech University, died March 16 in Blacksburg, Virginia, at the age of 98. Her obituary in the New York Times surveys her life.

Grene was a major scholar of philosophy who became known as one of the leaders in the philosophy of biology. When I first began (about 25 years ago) to think about the philosophy of biology--and especially the comparison of Aristotelian biology and Darwinian biology--I studied some of her writings and found them both illuminating and confusing.

Her book on Aristotle--A Portrait of Aristotle (1963)--was illuminating in showing how Aristotle's biology influenced all of his philosophic thought. But the book was also confusing, because while much of what she wrote suggested that Aristotle's biological thought was still defensible today, she also declared that the evolution of species was an "incontrovertible fact" that refuted Aristotle's science. From the evolution of species, it follows that:

"there is no being-what-it-is of each kind of thing, no ultimate and final definition of each natural class of substances, from which, with the necessary definiteness and precision, an Aristotelian science could take its start. We live for better or worse in an evolutionary universe, and, in the last analysis, evolution and Aristotelian science will not mix" (232).

But then in this same book, she seems to criticize Darwin and Darwinian science as unduly mechanistic and reductionistic. "The mysterious multifariousness of living nature, formerly a massive obstacle to mechanistic thinking, was transformed by Darwin's genius into an indefinite aggregate of random changes mechanically maintained. Life itself became machinery, made by no one for no purpose except barely to survive" (228). In later writings, however, she confessed that this was a misinterpretation of Darwinian science based on her then limited understanding of Darwin.

Grene's growing respect for Darwin in her later writings suggested to some readers that she saw common ground between Aristotle and Darwin. For example, David Depew (at the University of Iowa) is a scholarly student both of Aristotle and Darwin who co-authored a book on the history of the philosophy of biology with Grene. He suggests, in his contribution to The Philosophy of Marjorie Grene (The Library of Living Philosophers, 2002), that Grene was promoting a reconciliation between Aristotle and Darwin. But then Grene responded to him by denying this--"I don't want to effect a rapprochement between Aristotle and Darwin."

I am not enough a student of Grene's work to clear up this confusion. But I will say that reading her work--especially the writings collected in her book The Understanding of Nature (1974)--helped me to think through three critical issues--(1) reductionism, (2) teleology, and (3) the concept of species. Even if she herself saw no rapprochement between Aristotle and Darwin, she helped me to see some possible agreement between Aristotelian and Darwinian thinking on these three points. (Chapter 9--"The Ends and Kinds of Life"--of Darwinian Natural Right is my one piece of writing most pertinent to these issues.)

(1) Aristotle denies that living nature can be completely reduced to mere matter in motion. Although some biologists have argued for such materialist reductionism, this has never been achieved, and this failure points to the necessity for hierarchical explanations of life in which higher levels of formal organization cannot be simply reduced to lower levels. For example, the sequence of nucleotide bases in a DNA chain can convey genetic information only if the sequence has not been simply determined by physical-chemical laws.

(2) Although modern science may have refuted the idea of cosmic teleology--the idea that everything in the universe is directed to some hierarchy of ends or purposes--modern Darwinian science must still appeal to immanent teleology in that particular organic processes and particular species show some direction to particular ends. Reproduction, growth, feeding, healing, courtship, parental care for young--these and many other activities of organisms are goal-directed.

(3) Many Darwinians (such as Ernst Mayr and David Hull) have asserted that Aristotle's "essentialist" or "typological" conception of species has been refuted by the "populationist" conception of species in evolutionary science. If Aristotle believed that each species manifested an eternal "essence"--an unchanging set of traits that constitute the necessary and sufficient conditions for defining a species--then the Darwinian claim that all species evolve through history--coming into being and passing away--would seem to deny Aristotle's position.

As I have indicated in my post on David Buller's argument, one could conclude from this that there is no such thing as human nature, because the human species like every other species is a contingent product of evolutionary history that is too variable to constitute an eternal essence. Buller's reasoning is derived from David Hull. And I respond to Buller the way Grene responds to Hull. "Why, just because something does not last forever, should it lack a nature?," Grene asks. "That animals are born and die doesn't mean you can't tell one from another while it lasts, or even after it is dead." Although species are not eternally fixed, since they have evolved from ancestral species, that does not make them any less real during the time of their existence.

Richard Richards, a philosopher of biology at the University of Alabama, has suggested to me another way of stating this idea. Hull and Buller are correct to say that there are no necessary and sufficient conditions--essential conditions in the strong sense--that determine the membership of a living individual in a biological class. But there can still be "diagnostic" traits that distinguish one species from another. So even if there are no "essential" traits in the strong sense that define Homo sapiens, we can still see the stability in the diagnostic traits that identify human beings as human beings. And that's enough for speaking about "human nature." Moreover, Richards suggests, the view of Mayr and Hull that Aristotle was a strict "essentialist" in some strong sense is false.

The Darwinian affirmation of the historicity of life--that both living individuals and the species of life come into being and pass away--is compatible with an Aristotelian study of living nature and human nature. But many people will find this deeply disturbing. Those of a Platonic bent will worry that without eternal essences, everything collapses into a nihilistic flux. Those influenced by Biblical religion will worry that without an eternal Creator, evolving nature provides no enduring standards of thought or action.

But these worries from Platonic philosophy and Biblical religion arise from a false dichotomy of eternal fixity versus incoherent flux. Despite the historicity of nature in evolutionary time, the patterns in living nature are stable enough over long periods of time to enable our apprehension of natural kinds as enduring features of the world.

Shouldn't we consider ourselves lucky to have emerged from the natural history of life as the one form of life capable of studying that natural history and wondering what it all means?

I have elaborated some of these points in other posts.