In the 20th century, value inquiry had been greatly influenced by numerous impressive developments in biology, anthropology, and psychology, as well as evolutionary ethics in natural philosophy and new concepts in process theology. This progress in the special sciences includes fossil hominid discoveries, wild ape behavior studies, and genetic engineering research. The differences between the four pongids (orangutan, gorilla, chimpanzee, and bonobo) and the human species are narrowing in light of this new evidence, while recombinant DNA and the human genome project offer awesome possibilities for neolife forms and an indefinite life span for the human species. Moreover, neurological experiments are clarifying the direct relationship between the functioning material brain and all mental activity. The convergence of these remarkable advances in science and technology challenges entrenched beliefs and old values, resulting in the foundation for a new philosophical anthropology and a new conception of intellectual integrity.
Since the conceptual revolution of Darwinian evolution in the middle of the 19th century, the fixity of species and the traditional commitment to eternal truths have given way to a process view of life and the reevaluation of all values in light of empirical evidence, critical reflection, a cosmic perspective, and the evolutionary framework. Also, the new naturalist paradigm needs to take both cosmic entropy and species extinction seriously. No longer is earth or life on this planet or humankind itself viewed as the center of this universe. Furthermore, the scientific viewpoint critically evaluates all religious beliefs and theological concepts within the context of human sociocultural history. In brief, the human species must now be seen as a recent event within sidereal reality.
Grounded in organic evolution and human experience, value judgments hold both short-range and long-range consequences for the adaptation, survival, enrichment, and fulfillment of our own species. The conflict between facts and beliefs, as represented in the widening gap between scientific evolutionism and religious creationism, can only be resolved in terms of an open-minded acceptance of empirical evidence and rational deliberation. In fact, the value of dynamic integrity (as one shall see) becomes essential for the progressive development of evolving humankind.
Following the Age of Enlightenment, naturalists in the early decades of the 19th century began to take the scientific investigation of rocks, fossils, and artifacts seriously. Beyond denial, the empirical evidence argued for a conceptual view of earth history alarmingly different from a strict and literal interpretation of the biblical myth of Genesis. The result is a greater understanding of and deeper appreciation for time and change as a direct outgrowth of ongoing research in geopaleontology and bioanthropology. This paradigm shift, from fixity to evolution in natural history, has a devastating effect on all those cherished beliefs and traditional concepts that had given the human being its alleged unique place and special value in this universe.
Charles Darwin
As a young naturalist aboard the HMS Beagle, Charles Darwin (1809-1882) always remained open to a wide range of empirical evidence and personal experience during his 5-year voyage of discovery (1831-1836). Even though receiving a degree in theology, he was willing to doubt the story of Genesis while taking seriously both the new facts and the new concepts in several earth sciences, for example, historical geology, paleontology, biogeography, and comparative morphology. Likewise, his evolutionary interpretation of organic history in terms of “descent with modification” (from a common ancestor), through natural selection and sexual selection, incorporated the theoretical frameworks of Charles Lyell in historical geology and Thomas Malthus in population dynamics; their critical interpretations of rock strata and reproductive changes, respectively, had resulted in a scientific framework for uniting humankind with nature and history.
It is to Darwin’s lasting credit that his analytic abilities were supplemented by a rational imagination. Through abduction, that is, the creative interrelationship of facts and concepts, he was able to elevate his own methodology above a strictly empiricist approach in order to correctly investigate the natural world in terms of time and change (geology and biology). This open orientation of synthesis allowed him to bring about a conceptual revolution in terms of the biological evolution of all life on this planet.
A comprehensive and intelligible interpretation of organic history was first presented in the pivotal writings of Darwin, especially in his major book, On the Origin of Species (1859). Biological evolution replaced the eternal fixity of life forms. Yet in his epoch-making work, Darwin neither discussed human evolution nor considered the philosophical implications and theological ramifications surrounding the unshakable fact of organic evolution. Since our own species has emerged from an apelike form in the remote past, philosophers and theologians cannot ignore the reality that human beings themselves have created ethics, morals, and values within a natural environment and sociocultural milieu; one may speak of a human being as the evaluating animal, thereby distinguishing (but not separating) our own species from the apes and monkeys.
Clearly, scientific evolution both challenged and superseded the ideas and frameworks of Plato, Aristotle, Aquinas, Descartes, Kant, and Hegel (among many others). The certainty of previous values grounded in God-given laws or divine revelations could no longer be upheld by rigorous naturalists. As a result, the Darwinian conceptual revolution in modern science resulted in the emergence of both evolutionary ethics and pragmatic values in recent philosophy, as well as the emergence of sociobiology and evolutionary psychology in modern science.
Grappling with the implications of evolution, Thomas Huxley in England coined the word “agnostic” to express his own noncommittal position concerning the existence of God, while Ernst Haeckel in Germany advocated pantheism to express his dynamic worldview free from supernatural beliefs. In doing so, both evolutionists had acknowledged that the scientific fact of organic evolution has far-reaching consequences for those entrenched values of Western civilization that are grounded in traditional religion and theology. For over a decade, even Darwin himself had been reluctant to extend his theory of evolution to account for the origin and history of the human species (although Huxley and Haeckel did lecture on and write about human evolution during the 11 years following the publication of Darwin’s Origin volume).
Finally, in The Descent of Man (1871), Darwin himself argued that our species is closest to the great apes and shares a common ancestor, with the chimpanzees and gorillas, that would be found in the fossil record of Africa. The evolutionist now held that the human animal differs merely in degree, rather than in kind, from these two great apes; the bonobos of Africa had not been discovered yet, and the Asian orangutans now live only on the islands of Borneo and Sumatra.
Furthermore, Darwin claimed that the naturalistic basis of human morality had had its origin in those social instincts and altruistic feelings that have enhanced the adaptation and reproduction of evolving fossil apes and later protohominids followed by bipedal hominids. These instincts and feelings are visible in the behavior patterns of living primates (particularly in the four pongids).
The traditional static views of nature, life, and humankind have been discredited by science, reason, and a dynamic interpretation of this universe. Since the conceptual revolution of Darwinian evolution, a naturalistic framework has replaced all fixed, safe, and secure worldviews with a process perspective of material reality. Within a cosmic framework and from an evolutionary viewpoint, the narrowly conceived views of geocentrism and zoocentrism and anthropocentrism offered by previous philosophies have now been rigorously reevaluated and are found to be erroneous. Nevertheless, value inquiry does require a human-centered view of this universe if values are to be relevant, meaningful, and true for the human species.
Of the countless millions of species that have inhabited this planet (most of them now extinct), only one life-form has been able to philosophize on both its own existence, the natural environment, and ongoing history; one may speak of Homo sapiens sapiens as this evolving universe conscious of itself. More and more, through science and technology, the human species is capable of directing its ongoing evolution, as well as determining the future destiny of plant and animal forms on the earth and elsewhere. Today, one witnesses emerging teleology as a result of human intervention. This incredible power of control over life dictates that human beings must make those value judgments that will enhance their adaptation, survival, enrichment, and fulfillment: the wisdom of evolution shows that, as a species-conscious and evolution-aware form of life, humankind needs other plants, animals, and a suitable environment for its ongoing existence. Moreover, the inevitability of extinction is a brute fact for all life on earth and elsewhere.
Clearly, Charles Darwin had both intellectual and personal integrity; he was willing to change his scientific interpretation of nature as the integration of empirical evidence and rational concepts dictated. Darwin is exemplary of an open-minded and courageous naturalist, whose steadfast commitment to the controversial fact of organic evolution challenged both the engrained Aristotelian philosophy of fixed species and the dogmatic Thomistic theology of divine causality.
Ethics, Morals, and Values
Within the perspective of evolution, what about ethics and morals and values? Surely, the fact that our own species has evolved from a fossil pongidlike form of the remote past has something very significant to say about the human being as the bipedal, culture-bound, language-dependent, reflective ape (fifth pongid or third chimpanzee) and its social behavior patterns.
To decide what is right or wrong, philosophers offer ethical principles to guide human behavior, for example, Aristotle’s “golden mean” and Kant’s “categorical imperative” (the emphasis may be on individual fulfillment or social harmony). Within an ethical framework, human conduct is judged to be moral or immoral, that is, specific acts are held to be good or bad in terms of ethical judgments that consider the individual and/or social consequences of human behavior.
As a philosophical naturalist, the biology-oriented Aristotle (384-322 BC) appreciated the social value of friendship and recognized the relativity of excess and deficiency (from individual to individual) in a person’s striving to achieve excellence. Briefly, virtue ethics stresses the rational value of character development within a human society.
In sharp contrast to Aristotle, Immanuel Kant (1724-1804) ignored both evidence and experience in his quest for moral certainty. He universalized an act to determine its ethical worth, for example, he claimed that it is always wrong to tell a lie (otherwise, lying would have to be a moral law). Ultimately, Kant’s categorical imperative is grounded in cryptic theology; the ideas of God, free will, personal immortality, and a divine destiny for ethical persons are invoked to justify following the categorical imperative. For Kant, these ideas are grounded in an assumed, unknowable, noumenal world (a metaphysical assumption unnecessary for any rigorous scientist or thoroughgoing philosopher of evolution).
Of course, neither Aristotle nor Kant was an evolutionist. Today, for the pragmatic naturalist, both ethical principles and moral judgments are seen to be recent products of human biosocial evolution, and as such, the quest for certainty in human conduct becomes very problematic indeed (particularly if appeals to divine intervention and/or a transcendent world are rejected).
Friedrich Nietzsche
It was Darwin, the English scientist, who woke the German philosopher Friedrich Nietzsche (1844-1900) from his dogmatic slumber. Evolution offered a new framework within which Nietzsche could ruthlessly analyze the place of humankind in this universe. Having claimed that “God is dead!” is a truth about reality, he then called for a thoroughgoing reevaluation of all values. His analysis found the philosophical ideas and religious beliefs of European civilization to be false values that have resulted in the pervasive mediocrity of human culture (as he saw it). No doubt with Plato and Hegel in mind, Nietzsche wrote: “The will to a system: in a philosopher, morally speaking, a subtle corruption, a disease of the character…. I mistrust all systematizers and I avoid them. The will to a system is a lack of integrity.” For Nietzsche, constructing metaphysical systems for the sake of morality, particularly at a time witnessing the beginning of modern science with its bold evolutionism, was tantamount to childish deception.
Surely, however, one can be systematic and have integrity. Otherwise, it is difficult to see how the human species will endure in its never-ending struggle within evolving nature.
Nietzsche was correct to criticize a blind adherence to any static metaphysical system or rigid theological framework. In fact, he himself desired to systematize his own iconoclastic and dynamic worldview. Taking a cosmological stance, Nietzsche argued that both space and energy are finite, but time is eternal. Therefore, for him, this universe is a cycle of evolution and devolution; this cosmic cycle has been and will be repeating itself in an absolutely identical way throughout all eternity. Of course, there is no progressive evolution from cycle to cycle, since each cosmic cycle is the same.
Concerning interpretations of dynamic reality, the arc of evolution spans from mechanistic materialism to spiritual mysticism. Nietzsche’s own interpretation of evolution is grounded in creative vitalism. Furthermore, for Nietzsche, this universe is essentially the will to power and the human, all-too-human species is merely a temporary link between the past ape and the future overman (a superior being who will create new values beyond the traditional conceptions of good and evil).
Nietzsche said “Yes!” to the eternal recurrence of the same reality. Moreover, in this dynamic universe
of organic evolution, he stressed the essential value of human creativity and, as an atheist, challenged the human species to create new values that are free from religion and theology. Invoking his eternal recurrence perspective, Nietzsche taught that an individual must affirm life by willing to live it as if each choice one makes is a judgment for all eternity. Consequently, for him, each moment has eternal value.
Unfortunately, Nietzsche failed to clarify his own views on truth, science, and naturalism. Even so, this iconoclastic philosopher did have integrity, as is demonstrated in his scathing criticism of outmoded beliefs and in his desire to incorporate the findings of science and the use of reason in order to verify his awesome idea of the eternal recurrence of this same universe. It was Nietzsche’s steadfast commitment to both overcoming mediocrity and the quest for wisdom that elevated his cosmic vision above the pervasive pettiness of human existence (as he interpreted it).
Naturalism and Pragmatism
Before the writings of John Dewey (1859-1952), the pragmatists Charles Sanders Peirce and William James had been influenced by the evolutionary movement in the special sciences. All three thinkers represented the crucial transition from religious idealism to philosophical naturalism in American thought.
For the modern pragmatist as evolutionary naturalist, science has epistemological priority, and matter (energy) is the ontological makeup of this dynamic universe. This practical philosophy does not dogmatically rule out theoretical constructs or rational speculations, but it does require factual evidence to justify objective truth-claims about our species, human society, and the natural world.
In step with the new logic of evolution, Dewey developed a pragmatic naturalism that stressed a need for philosophy to accept the advances in science. In particular, the discoveries of Galileo and Darwin had reshaped earlier interpretations of concrete nature. And for Dewey, philosophy has an obligation to incorporate these new scientific findings into its worldview.
In his insightful essay “The Influence of Darwin on Philosophy” (1910), Dewey pointed out the sharp contrast between change and fixity. He held that a modern thinker must acknowledge the superiority of the scientific method, as well as the flux of both human knowledge and nature itself. With sensitivity to the modern situation, Dewey wrote: “We live in the twilight of intellectual transition.” Like Nietzsche, Dewey knew that the conceptual revolution of Darwinian evolution foreshadowed the transformation of false beliefs, old values, and static worldviews.
Ignoring science, many phenomenologists and existentialists had adopted a subjectivist stance in sharp contrast to the naturalist attitude, not to forget the antiscientific menace of fundamentalism and the intellectual nuisance of postmodernism. In the tradition of philosophical naturalism, Marvin Farber (1901-1980) taught that the human species is totally within nature; the fact of evolution had successfully shaken him free from a narrowly conceived phenomenology (which he eventually came to see as a limited methodology incapable of delivering a true ontology, sound epistemology, and humanist ethics).
Farber appreciated the obvious value of Darwinism for a sound naturalist philosophy. Reflecting on the liberating influence of evolutionism from spiritualism, he wrote: “Although philosophical criticism had long before anticipated this result, it was the large array of scientific evidence offered by Darwin which delivered the most distressing blow to the supernaturalist.” Ultimately, the Farberian outlook is grounded in humanist values and pervasive materialism.
Despite their adherence to social change and organic evolution, John Dewey and Marvin Farber still clung to an outmoded idea. Although rejecting Hegel’s idealism, Dewey retained an ambiguous conception of God inconsistent with a succinct naturalism; even so, he was not a practicing believer. Although rejecting Husserl’s idealism, Farber remained sympathetic to Marxism even though it stifled intellectual creativity; moreover, he had never visited the Soviet Union. Nevertheless, by embracing science and reason, each philosopher did represent a significant degree of dynamic integrity.
Dynamic Integrity
An enlightened thinker is acutely aware of deep space, deep time, deep evolution, and deep psychology. Unfortunately, recent philosophy is usually detached from the incredible discoveries and awesome perspectives of modern science. This universe encompasses billions of galaxies; Earth is billions of years old; the process of organic evolution results from those random variations that occur in the biochemical complexity of the DNA molecule; and unconscious activity motivates human behavior. Furthermore, beneath all the myriad evaluations of the human being lies a deep value: this is the virtue of integrity. But as a direct result of scientific cosmology and modern anthropology, no longer can the human species cling to a static worldview, that is, no longer can it be dogmatically committed to a myopic and closed philosophy, fixed moral maxim, or universal ethical principle (Aristotelian fixity and Kantian certainty have given way to evolutionary pragmatism).
It is now necessary for emerging humankind to recognize the quintessential need for a dynamic integrity that understands and appreciates the obvious fact of evolving nature while remaining in step with the advances of science and technology. Dedicated to a neo-Enlightenment and open inquiry, dynamic integrity integrates scientific findings, process cosmology, and evolutionary naturalism into a comprehensive and intelligible philosophical anthropology that encourages both creating and reassessing human values. Such an interdisciplinary attitude fosters a holistic character that is amenable to social change, critical dialogue, and pervasive investigation.
Yet, dynamic integrity must mean more than simply living an ethically integrated life or merely having a morally unified self. Instead, it entails an open-minded and open-ended commitment to science, reason, compassion, new perspectives, and the betterment of the human species. In principle, dynamic integrity is evolution based, for example, it acknowledges the unity of self, the unity of humankind, the unity of life, and the unity of this universe.
Dynamic integrity requires the creative union of thought and action. A person has dynamic integrity when his or her actions are not only based on empirical evidence and logical reflection but also when these actions contribute to the adaptation, survival, enrichment, and fulfillment of human beings. Consequently, in terms of ethics and morals, dynamic integrity is both deontological and teleological in nature: there is a duty to accepting scientific evidence, as well as an ongoing commitment to improving the human species by increasing knowledge, freedom, happiness, and longevity.
Briefly, dynamic integrity is both an attitude of mind and an approach to life that acknowledges the immensity of this universe, the brevity of human existence within it, and the ongoing need to enhance our species through scientific knowledge, critical thought, and resolute effort.
In evaluating their creative lives, both Darwin and Nietzsche represented a commitment to the essential value of dynamic integrity: Darwin revolutionized science through his giving attention to the facts of geobiology and their far-reaching implications for life in terms of evolution, while Nietzsche rejected the falsehoods and mediocrity of modern civilization and, subsequently, challenged the human species to create new values.
Pierre Teilhard de Chardin
The geopaleontologist and mystic Pierre Teilhard de Chardin (1881-1955) demonstrated dynamic integrity by embracing evolution, even though he was silenced by the Roman Catholic Church for his unorthodox ideas and perspectives. This courageous Jesuit priest had accepted and incorporated into his faith the facts from geology, paleontology, biology, and anthropology (even though this convergence of empirical evidence required a new interpretation of humankind within nature that challenged traditional beliefs and old values). In sharp contrast, many of today’s creationists choose to reject or ignore any empirical evidence that may discredit their faith, theology, or perspective.
Unfortunately, the Harvard scientist Stephen Jay Gould lacked dynamic integrity when, without sufficient evidence, he implicated Teilhard in the infamous Piltdown hoax and thereby besmirched the Jesuit priest’s reputation. Furthermore, Gould criticized Teilhard’s theistic evolutionism. Ironically, this is despite the fact that Gould himself clung to an outmoded and unwarranted ontological dualism by advocating the existence of two separate realms of inquiry: the natural world of the scientist and the transcendent world of the theologian (at least Teilhard had attempted to bridge these two realms in terms of an evolving and converging spiritual panentheism). If one takes Gould seriously and assumes that these two different realms do exist, then how do they influence each other in any meaningful way? Under rigorous scrutiny, Gould’s dualism quickly becomes completely superfluous for the evolving human species.
Regrettably, because of his dualistic approach to naturalistic neo-Darwinism, Gould is being used by biblical fundamentalists and religious creationists to discredit the fact of evolution. A rigorous evolutionist (with dynamic integrity) realizes that there is only this material universe, and that the emerging human species is a product of, dependent upon, and totally within it.
The spread of fundamentalism and creationism in our modern world clearly illustrates a growing resistance to science and reason, not to mention a lack of vision for the future of humankind. Unfortunately, the gap between facts and beliefs continues to widen. In particular, the rejection of an evolutionary framework by some philosophers and many religionists clearly demonstrates that internal consistency alone in a worldview is not the road to truth and wisdom. In the ongoing quest for both truth and wisdom, dynamic integrity is always necessary.
And today, more and more, the potentially rational and sometimes compassionate human species needs to value those new ideas and collective actions that will contribute to its survival and fulfillment (in sharp contrast, by rejecting science and reason, all supernatural worldviews are bound to fail because their beliefs will be discredited by empirical evidence). Evolutionism forces one to look at this universe, life on earth, and the human species in a radically new way. Change is an invitation to improvement, and humankind must now choose evolution over stagnation. To save biodiversity and civilization, it is the deep value of dynamic integrity that becomes the axiological foundation for the emerging human species on earth, as well as its ongoing evolution elsewhere in this universe.
Pierre Teilhard de Chardin had called for an ultra-anthropology that views our species within an ever-widening comprehensive framework. In the future, scientists and philosophers will need to remain open to compelling evidence and progressive concepts if their thoughts and actions are to be relevant, meaningful, and true. For the evolutionary naturalist, philosophical inquiry must be in step with scientific discovery. In short, dynamic integrity underpins both pragmatism and materialism. As such, dynamic integrity is the essential value for wise social conduct and purposive creative intelligence throughout the centuries to come.
Quo Vadis
Our hominid species is the result of 7 million years of Darwinian evolution from fossil apelike forms to the human being of today. Only a complete disregard for modern geopaleontology and bioanthropology would prevent one from recognizing the established fact that the human being represents a recent species within primate evolution. For an evolutionist, our own species is the successful great ape that dominates this planet because of its sustained bipedality, social behavior, material culture, and symbolic language as articulate speech.
But the human species is not a fixed animal within organic history and sociocultural development. Furthermore, humankind is not nailed to the earth. Despite global convergence but with critical optimism, one may speak of the future divergence of our species beyond this planet as the human being becomes the cosmic ape among the stars.
As the human species continues to evolve on earth and elsewhere, space exploration along with nanotechnology and genetic engineering offer a Nietzschean vision: the emergence of godlike overbeings in the ages to come. No doubt, the human being has only glimpsed the awesome powers of science and technology in terms of both manipulating and directing the process of organic evolution. Our future generations will probably enjoy an indeterminate life span and see the artificial creation of neolife forms (i.e., new species of plants and animals), as well as the alteration of the human species for its adaptation to and survival in new environments, for example, living in outer space and on other worlds.
The planetary fallacy (as this author calls it) erroneously maintains that life, organic evolution, and intelligence are restricted only to the earth. Such a myopic viewpoint rejects the probability of both exobiology and exoevolution in this dynamic universe. Admittedly, the serious consequences of ongoing evolution challenge those values that many adhere to today, especially the claim that the human species is absolutely unique in reality. Overcoming the planetary fallacy, one should embrace a truly cosmic perspective in which humankind has the courage to explore outer space and to evolve into a superior form of life in terms of both intelligence and technology. As such, one may speak of the emerging cosmic ape as the brave and curious terrestrial human species ventures into sidereal space (a momentous transition for planetary life that has already begun). Of course, our cosmic destiny will require that humankind solve those future problems that are inherent in adaptation, survival, and evolution among the stars.
For the pragmatic naturalist, meaning and purpose in human life are derived from, and value judgments are made within, material existence. No doubt, continued progress in science and technology, as well as an ever-widening perspective, will result in a reevaluation of our present values. Surely, many centuries from now, the old values of the Judeo-Christian-Islamic religions and Eastern philosophies will be replaced by new values (assuming that the human species survives on this planet and/or elsewhere). And there is always the crucial need for ongoing inquiry in order for humankind to overcome both intellectual stagnation and psychological boredom.
Likewise, a community of inquirers will be necessary for the continuing evolution of Homo sapiens futurensis as it engineers this solar system and others for its survival and fulfillment among the myriad of galaxies throughout this universe. For the success of this cosmic adventure, humankind must affirm both the joy of life and the value of existence.
Furthermore, the human species must overcome the omega illusion (as this author sees it). In the 20th century, Pierre Teilhard de Chardin offered a mystical vision of the final end-goal for human evolution on earth and then beyond it. His speculations appeal to the psychological needs and emotional desires of the human species (especially in light of the certainty of death). But the wish for personal immortality is no proof that such a status is true or even possible.
Without evolution, nothing makes sense. The pragmatic naturalist acknowledges the development of our modern worldview, from Julian Huxley’s religion without revelation to Richard Dawkin’s evolution without theology; one may speak of the development of values from the sacred to the secular. In this context, the backsliding from material evolution by some renowned thinkers is deeply regrettable and clearly demonstrates a failure of nerve. Of course, there is always the human need for love, compassion, and responsibility (aspects belonging to the naturalist outlook and dynamic integrity).
Finally, there is always the need to establish ethical guidelines for scientific research that must value nature, life-forms, humankind, and critical thought. Since the groundbreaking contributions of Charles Darwin and Friedrich Nietzsche, the brute fact of organic evolution and the empirical findings of the special sciences continue to reinforce a materialist framework that is paving the way for a cosmic neo-Enlightenment free from nonsense, ignorance, superstition, and obscurantism. With dynamic integrity as its essential guideline, the pragmatic human species will continue to make substantial progress in terms of both utilized scientific truth and shared philosophical wisdom.
References:
- Darwin, C. (2000). The autobiography (Introduction by H. James Birx). Amherst, NH: Prometheus Books.
- Dewey, J. (1965). The influence of Darwin on philosophy and other essays in contemporary thought. Bloomington: Indiana University Press.
- Farber, M. (1968). Basic issues of philosophy: Experience, reality, and human values. New York:
- Harper Torchbooks. Gould, S. J. (1997). Nonoverlapping magisteria. Natural History, 106(2), 16-22.
- Haeckel, E. (1992). The riddle of the universe (Introduction by H. James Birx). Amherst, NH: Prometheus Books.
- Nietzsche, F. (1993). Thus spake Zarathustra (Introduction by H. James Birx). Amherst, NH: Prometheus Books.
- Rachels, J. (1991). Created from animals: The moral implications of Darwinism. New York: Oxford University Press.
- Teilhard de Chardin, P. (1975). The phenomenon of man (2nd ed.). New York: Harper Colophon.
