It had long been observed that animals and other living things are particularly well-adapted to the environments in which they live. Prior to November 24, 1859 — 150 years ago today — the best explanation for this amazing phenomenon was that they had been designed specifically for that purpose.

Design implied a designer, and demonstrating the existence of this designer through reasoning is known as the design argument. The design argument is the cornerstone of natural religion or natural theology — the study of God as disclosed in His creation, and then into deriving evidence from the creation of His providence and beneficence.

The design argument has been around since at least the Ancient Greeks. In Laws (c. 350 BCE) Plato demonstrates not only that the Gods exist, but that they care about us and “guard our highest interests.” They cannot be tempted otherwise: The Gods “would never betray justice for the sake of gifts which unjust men impiously offer them.” (What Plato does not demonstrate, however, is monotheism. The Gods he speaks of are certainly not the raucous and often immoral characters of Greek mythology, but they shouldn’t be confused with the Christian heavenly father either.)

“How could the sea-tides and the confined waters in the straits be affected by the rising and setting of the moon?” Cicero asks in The Nature of the Gods (c. 44 BCE). “Or the diverse course of the stars be maintained in the single rotation of the entire heavens? What is certain is that these processes could not take place through harmonious activity in all parts of the universe, unless they were each embraced by a single divine, all-pervading, spiritual force.”

You can find a gorgeous statement of natural theology in the Old Testament — “The heavens declare the glory of God; and the firmament sheweth his handywork.” (Psalms 19:1) — and a clunkier one in a letter by Paul: “Because that which may be known of God is manifest in them; for God hath shewed it unto them. For the invisible things of him from the creation of the world are clearly seen, being understood by the things that are made, even his eternal power and Godhead.” (Romans 1:19-20). So begins the long but rocky Christian tradition of natural theology.

In the thirteenth century, Dominican friars, most notably Thomas Aquinas (1225 – 1274), began integrating Aristotle into Christian theology, and from this synthesis essentially created the modern study of science in the form of natural philosophy. From Thomas Aquinas right into the nineteenth century, natural theology became the raison d’être of natural philosophy. Natural philosophy was very explicitly the study of God’s creation, and natural theology was the application of this knowledge to a greater understanding of God.

But natural theology by itself was insufficient. In isolation, natural theology was considered inadequate and even dangerous. For resolving those many crucial ambiguities that may still be lingering after the reason of natural theology is exhausted, it was necessary to consult the Bible. Natural theology had to be balanced with revealed theology. Once you’ve established the existence and nature of God through natural theology, you can then pursue His words through the study of scripture.

Natural theology and revealed theology thus became the two interlocking pillars of Christianity. Natural theology was particularly an important part of intellectual thought in Great Britain starting around the time of the Revolution of 1688. It's possible that the Revolution impressed on people the need to find a philosophy and theology that reconciled all religions, and that was the study of nature. Or perhaps it had something to do with the publication of Isaac Newton's Philosophiæ Naturalis Principia Mathematica the year before in 1687. Certainly the development of the telescope (earlier in the century) and Robert Hooke's popularization of the microscope in the Micrographia (1665) played a role in allowing natural philosophers to explore the far-away and the very-small as never before.

As naturalists peered ever deeper into living things, they saw miniature complex structures and intricate mechanisms far beyond the engineering capabilities of man. Just as the astronomers had found laws and order in the workings of the clockwork universe, naturalists were finding order amid the complexity of life.

Prior to the seventeenth century, design arguments were vague and general. Now they became very specific as each latest scientific discovery bolstered anew the fact of God’s existence and beneficence. Through the end of the seventeenth century and into the eighteenth century, natural philosophy and natural theology matured in unison. Popular books were published that explored these connections, such as the Wisdom of God Manifested in the Works of the Creation (1691) by English naturalist and ordained minister John Ray (1627 – 1705). Ray had done much of his scientific work in describing and classifying species. In this book he showed how form and function in living things were perfectly meshed.

Over a hundred years later, the same message can be found in Natural Theology, or Evidence of the Existence and Attributes of the Deity, Collected from the Appearances of Nature (1802) by Archdeacon William Paley (1743 – 1805). Natural Theology remains quite readable and enjoyable. (The first edition was republished a few years ago by Oxford World's Classics with an information introduction and extensive notes.) In this one book, Paley summed up all the prevailing arguments that had convinced almost everyone in the 18th century of the existence of God, even thinkers regarded then (and now) as extreme skeptics, such as Voltaire and Thomas Paine.

Natural Theology begins with the famous watch and its examination, leading to the inference

that the watch must have had a maker; that there must have existed, at some time and at some place or other, an artificer or artifiers who formed it for the purpose which we find it actually to answer; who comprehended its construction, and designed its use. (Ch. 1)

But Natural Theology is not about watches,

for every indication of contrivance, every manifestation of design, which existed in the watch, exists in the works of nature; with the difference, on the side of nature, of being greater and more, and that in a degree which exceeds all computation. (Ch. 3)

Paley then embarks on extensive descriptions of many of the marvels of the natural world, beginning with the most amazing of them all: the human eye. Paley's enthusiasm is infectious, and it is easy to understand how popular and persuasive this book was.

Yet, around Chapter XXIII (entitled "Of the Personality of the Deity") Paley makes an enormous leap. He is not satisfied simply with demonstrating that some kind of designer exists. He needs to go further and show that this designer has certain attributes: "omnipotence, omniscience, omnipresence, eternity, self-existence, necessary existence, spirituality." (Ch. XXIV) He has to demonstrate the "goodness" of the designer, and Paley finds evidence of this as well:

It is a happy world after all. The air, the earth, the water, teem with delighted existence. In a spring noon, or a summer evening, on whichever side I turn my eyes, myriads of happy beings crowd upon my view. (Ch. XXVI)

And perhaps Paley is revealing another reason why natural theology was so popular among England's comfort class: The beauty of England's scenery, and the comparative lack of earthquakes, volcanoes, and extreme weather, made God's creation seem a particularly pleasant and amenable one.

This is not to imply that the legitimacy of the design argument was never challenged, but doing so required a fearless intellect of the highest order. Natural theology received its most thorough thrashing at the hands of Scottish philosopher David Hume (1711 – 1776). Throughout his life, Hume had maintained a strong skepticism regarding religion. His dissection of miracles — originally suppressed in A Treatise of Human Nature (1739 – 40) but later appearing as Chapter 10 of An Enquiry Concerning Human Understanding (1748) — to this day remains a favorite of anthologists of skeptical writings.

Hume focused specifically on natural theology and the design argument in the posthumously published Dialogues Concerning Natural Religion (1779). Although Hume had written the first draft two decades earlier, he withheld publication due to the incendiary nature of the work and the advice of his friends. The first problem that Philo (the skeptic character in the Dialogues) takes on is the use of analogy. We commonly employ analogy when comparing similar causes that produce similar effects. But man-made machines and the universe are so dissimilar as to make any analogy invalid, particularly considering that man is part of the very universe that his analogous being (God) created:

If we survey a ship, what an exalted idea must we form of the ingenuity of the carpenter, who framed so complicated useful and beautiful a machine? And what surprise must we entertain, when we find him a stupid mechanic, who imitated others, and copied an art, which, through a long succession of ages, after multiplied trials, mistakes, corrections, deliberations, and controversies, had been gradually improving. Many worlds might have been botched and bungled, throughout an eternity, ere this system was struck out: Much labour lost: Many fruitless trials made: And a slow, but continued improvement carried on during infinite ages in the art of world-making. (Hume, Dialogues Concerning Natural Religion, Part V)

And what does it imply when we learn that the ship was made not by a single person, but by a large number of men, each specialized in a particular aspect of the total job? Employing the analogies and "logic" of natural theology, it's not even possible to prove the legitimacy of monotheism!

Nor is Philo impressed that the various parts of plants and animals seem precisely designed for their uses. In a form of the anthropic principle, he argues that living things could not live otherwise:

It is in vain … to insist upon the uses of the parts in animals or vegetables and their curious adjustment to each other. I would fain know how an animal could subsist, unless its parts were so adjusted? Do we not find, that it immediately perishes whenever this adjustment ceases, and that its matter corrupting tries some new form? It happens, indeed, that the parts of the world are so well adjusted, that some regular form immediately lays claim to this corrupted matter: And if it were not so, could the world subsist? Must it not dissolve as well as the animal, and pass through new positions and situations; till in great, but finite succession, it falls at last into the present or some such order? (Part VIII)

Well, obviously that's not entirely satisfactory either.

Charles Darwin (1809 – 1882) read Paley at Cambridge. It was part of the curriculum. "I did not at that time trouble myself about Paley's premises," he later wrote in his Autobiography, "and taking these on trust I was charmed and convinced by the long line of argumentation." Darwin might have ended up as a doctor like his father if he hadn't found the experience of witnessing an operation to be intolerable, and he might have become a country parson if had been more comfortable with the 39 Articles of Religion of the Church of England.

Instead, he got a unique opportunity to serve as naturalist on the HMS Beagle for a trip around the world that lasted nearly five years. This was truly the formative experience in Darwin's life. He discovered nature not quite as polite as the English countryside. He witnessed a volcano and an earthquake. He saw all kinds of people. He examined geology and nature in much detail. And he read Charles Lyell's Principles of Geology which posited a very long age of the Earth and many changes over those eons. It got him thinking about species.

In July 1837, Darwin began a notebook on the "transmutation of species," that is, how one species can change into another. At the time, the prevalent belief among geologists and naturalists was that within a species, there could be much variety, but species themselves were fixed and immutable. It was well known from the study of geological strata that at distant times in the past, some species seemed to come into existence and other seemed to disappear, but there was no good explanation how these new species were created or where the old ones went.

To be sure, some natualists believed that species could transmute from one to another, from simpler forms to more complex forms. Darwin's own grandfather Erasmus had believed so. So did Buffon and Lemarck. But the suggested mechanism of mutation usually involved inherited characteristics, and this process itself seemed too vague and flawed.

In 1838, while reading Thomas Robert Malthus's An Essay on the Principle of Population (1798 – 1826) Darwin hit upon the solution. He found a process that explained adaptation and apparent design in living things but which did not rely upon a designer.

Darwin knew that his theory would be controversial, and that he would likely be intellectually pilloried for it, and he also knew that his pious wife Emma would be upset. Before going public, he wanted to amass as much information as he could to support his ideas. But fearing he might die first, in 1842 Darwin wrote a short Sketch describing what he was now calling natural selection, and in 1844 he expanded that into a longer Essay. If he were to die, his wife was to have this essay published. (These two documents were first published in 1909 under the editorship of Darwin's son Francis. I have another book containing these two essays entitled Evolution by Natural Selection published by Cambridge University Press in 1958.)

In 1856, Darwin began writing a book entitled Natural Selection that promised to be very long. But it was never finished. In June 1858 he received a paper in the mail by a young naturalist Alfred Wallace describing basically the same theory as Darwin had developed over the past twenty years. It was obviously time to go public. In July, a presentation to the Linnean Society of London presented papers from both Darwin and Wallace, and then Darwin got busy on what he thought of as an "abstract" for the much larger book.

That "abstract," published 150 years ago today on November 24, 1859, is On the Origin of Species by Means of Natural Selection, or the Preservation of Favoured Races in the Struggle for Life. (In this context the word "races" is used in an old sense to mean "varieties" within a species. In the text of the book, "variety" is used almost exclusively and "race" only seldom.)

On the Origin of Species went through many editions and eventually lost the "On" at the beginning of the title. But it's become more common in recent decades to read the first edition of the book to get the full sense of its historical impact. In 1981, Harvard University Press published a nice facsimile edition with an introduction by Ernst Mayr, and of course you can view the first edition online.

But spend a little money and you can get something really nice. Earlier this year, Harvard University Press published a terrific book entitled The Annotated Origin containing a very readable facsimile of the first edition along with a multitude of helpful annotations by Professor James T. Costa. This book is likely to be the preferred text for reading On the Origin of Species for many decades to come.

Darwin begins On the Origin of Species by describing not the workings of nature, but domesticated animals, specifically pigeons and those lovable domesticated wolves known as dogs. Pigeons and dogs display a wide range of variety, and if we didn't know any better, we might assume that these different varieties are actually different species. Yet, naturalists agreed that all domesticated pigeons are descended from the rock-pigeon, and likewise all dogs are descended from (Darwin believed) several wild stocks.

How does it happen that these domesticated animals have such wide variety within a single species? Human beings have fabricated these varieties through the process of breeding. Generation by generation, animals are born that have natural variety. The breeders selectively mate the ones with the qualities they want.

The key is man's power of accumulative selection: nature gives successive variations; man adds them up in certain directions useful to him. In this sense he may be said to make for himself useful breeds.... If selection consisted merely in separating some very distinct variety, and breeding from it, the principle would be so obvious as hardly to be worth notice; but its importance consists in the great effect produced by the accumulation in one direction, during successive generations of differences absolutely inappreciable by an uneducated eye — differences which I for one have vainly attempted to appreciate. (pgs. 30, 32 — all page numbers are from the first edition)

This is artifical selection — artificial because people are doing the breeding. Yet, artificial selection is obviously capable of much power to fabricate extreme varieties, as anyone visiting the dog-run at their local park can attest.

With natural selection, it is nature herself doing the breeding. As Darwin learned from Malthus, living things are in a struggle for survival in competition for finite food sources. For a particular species, there is natural variety. If a particular characteristic helps an individual survive and procreate, that characteristic will be passed on to that individual's offspring.

It may be said that natural selection is daily and hourly scrutinising, throughout the world, every varieties, even the slightest; rejecting that which is bad, preserving and adding up all that is good; silently and insensibly working, whenever and wherever opportunity offers, at the improvement of each organic being in relation to its organic and inorganic conditions of life. We see nothing of these slow changes in progress, until the hand of time has marked the long lapse of ages, and then so imperfect is our view into long past geological ages, that we only see that the forms of life are now different from what they formerly were. (pg. 84)

Or as he succinctly expressed it later in the book, "one general law, leading to the advancement of all organic beings, namely, multiply, vary, let the strongest live and the weakest die." (pg. 244) It sounds cruel, but that's the way nature works. (And there's no reason for our social organizations to be structured similarly.)

Darwin didn't see a sharp distinction between varieties and species: "varieties are species in the process of formation, or are, as I have called them, incipient species." (pg. 111) As two varieties diverge, they eventually become different enough to be categorized as separate species. Working backwards, the whole tree of life collapses into primeval life forms. The common classification of animals and plants into groups is actually but unknowingly based on inheritance:

It is a truly wonderful fact — the wonder of which we are apt to overlook from familiarlity — that all animals and all plants throughout all time and space should be related to each other in group subordinate to group, in the manner which we everywhere behold — namely, varieties of the same species most closely related together, species of the same genus less closely and unequally related together, forming sections and sub-genera, species of distinct genera much less closely related, and genera related in different degrees, forming sub-families, families, order, sub-classes and classes. (pg. 128)

(Creationists still treat species as fixed, immutable barriers to change. It has become common for creationists to show how "open-minded" they are by expressing their belief that changes can occur within a species, but in making that distinction, they demonstrate that they reject Darwin's entire treatise, and hence are 150 years behind the scientific times. Here, for example, is Republican Senator Sam Brownback of Kansas in an op-ed piece in the N.Y. Times, with emphasis added by me: "If belief in evolution means simply assenting to microevolution, small changes over time within a species, I am happy to say, as I have in the past, that I believe it to be true.")

Reading the first edition of On the Origin of Species is a thrilling experience as the reader witnesses Darwin solving one of the greatest puzzles of existence — the "mystery of mysteries" as Sir John Herschel called it. (Origin, pg. 1) Darwin had been working on this concept of natural selection for about twenty years, so he had lots of time to collect evidence and perform his own experiments, No "arm-chair naturalist," Darwin raised pigeons, grew lots of plants, and performed odd experiments (one of which I quoted yesterday).

He also had time to ponder problems, and several chapters in On the Origin of Species address these issues. Given its prominent position in Paley's Natural Theology of course Darwin had to take on the big one. Creationists are fond of quoting this passage:

To suppose that the eye, with all its inimitable contrivances for adjusting the focus to different distances, for admitting different amounts of light, and for the correction of spherical and chromatic aberration, could have been formed by natural selection, seems, I freely confess, absurd in the highest possible degree. (pg. 186)

But this sentence is followed by Darwin's full confidence in the power of natural selection to create an eye beginning with simple light-sensitive nerves, and he describes the various steps in how this might have come about. It is extraordinary how well Darwin thought it all through, and how much it got right. He didn't know about genetics. Gregor Mendel didn't publish his research on peas until 1866 and even then it was widely unknown.

Of course, natural selection didn't disprove natural theology. Like everything else, natural theology adapted to its new environment. But what Darwin did was provide an alternative explanation for the appearance of design in the natural world — an explanation built upon concepts that virtually everyone can understand, which are very plausible, and which do not involve any type of "magic."

Does the blind mechanical process of natural selecion take some of the "wonder" out of life? I think not, but I will let Darwin himself express his continued wonder with nature in the famous last paragraph of his book:

It is interesting to contemplate an entangled bank, clothed with many plants of many kinds, with birds singing on the bushes, with various insects flitting about, and with worms crawling through the damp earth, and to reflect that these elaborately constructed forms, so different from each other, and dependent on each other in so complex a manner, have all been produced by laws acting around us. These laws, taken in the largest sense, being Growth with Reproduction; Inheritance which is almost implied by reproduction; Variability from the indirect and direct action of the external conditions of life, and from use and disuse; a Ratio of Increase so high as to lead to a Struggle for Life, and as a consequence to Natural Selection, entailing Divergence of Character and the Extinction of less-improved forms. Thus, from the war of nature, from famine and death, the most exalted object which we are capable of conceiving, namely, the production of the higher animals, directly follows. There is grandeur in this view of life, with its several powers, having been originally breathed by the Creator into a few forms or into one; and that, whilst this planet has gone cycling on according to the fixed law of gravity, from so simple a beginning endless forms most beautiful and most wonderful have been, and are being, evolved.

Earlier Entries in the Sesquicentenniality Series

1859 Books: “Rubáiyát of Omar Khayyám” (1/15/2009)

1859 Books: George Eliot’s “Adam Bede” (2/1/2009)

1859 Books: John Stuart Mill’s “On Liberty” (2/26/2009)

1859 Books: Anthony Trollope’s “The Bertrams” (3/29/2009)

1859 Art: Frederic Church’s “The Heart of the Andes” (4/27/2009)

1859 Journalism: Harriet Martineau’s “Female Industry” (5/30/2009)

1859 Science: John Tyndall and the Greenhouse Effect (6/10/2009)

1859 Books: George Meredith’s “The Ordeal of Richard Feverel” (6/20/09)

1859 Books: Tennyson’s “Idylls of the King” (7/17/09)

1859 Music: Richard Wagner’s “Tristan und Isolde” (8/30/2009)

1859 Books: Harriet Wilson’s “Our Nig” (9/5/2009)

1859 Speeches: Prince Albert’s Address to the BAAS (9/14/09)

1859 Books: Samuel Smiles’ “Self-Help” (9/29/09)

1859 Crusades: John Brown’s Raid on Harpers Ferry (10/16/09)

1859 Books: Charles Dickens’ “A Tale of Two Cities” (11/21/09)