William Paley, 1791.
William Paley was an erudite 18th-century English clergyman who is best known today for weighing-in on what Charles Darwin would call, decades later, "the species question": where do living (and fossil) species come from, and how do they come to be so exquisitely adapted to their place in "the economy of nature?" Paley wrote, among other things, the elegant and influential book Natural Theology. In it, he eloquently presents a sophisticated argument for creationism, aka intelligent design. Even today it is an impressive argument on its face. He begins by imagining someone encountering a pocket watch on the ground. Knowing nothing at all about it, he perceives that its intricate, purposeful mechanism could not come about by chance: it must have a designer. So, then, the still-more-intricate and wonderful mechanism of a living thing, so tuned to its place in the economy of nature, must also have a designer. Later in his book, Paley similarly discusses in detail the intricate design of the eye, and the clockwork precision of the workings of the heavenly bodies.
One side effect of Paley's work was that the study of natural history became important to clergymen, who thereby explored God's creation. Charles Darwin was introduced to Paley as part of his university education, and early on in his own career he found Paley very convincing.
I came across an excerpt from Natural Theology while I was writing a high school biology unit on evolution, and was inspired to write a reply to his argument, in approximately the same style, again using the discovered watch, but also evidence Paley didn't consider, and of course evolutionary theory. To be fair, Paley wrote Natural Theology the same year Charles Darwin was born, Darwin's Origin of Species came out fifty years later, and the theory of evolution by natural selection did not completely overcome competing theories until another half-century had passed. (When an undergraduate discovering Darwin's Origin of Species in the university bookstore, I was struck by fellow-feeling: I was born one hundred years after its publication, and was then the same age as Darwin when he embarked on HMS Beagle.) So Paley held sway on "the species question" for most of a century.
Excerpt from Natural Theology
When we come to inspect the watch, we perceive...that its several parts are
framed and put together for a purpose, e.g. that they are so formed and
adjusted as to produce motion, and that motion is so regulated as to point out
the hour of the day; that, if the different parts had been differently shaped
from what they are, if a different size from what they are, or placed after any
other manner, or in any other order than that in which they are placed, either
no motion at all would have been carried on in the machine or none which
would have answered the use that is now served by it...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.
A Reply to Natural Theology
diverse sizes and shapes and composed of gears similar to those in the watch,
but variously differing in configuration and complexity, some indeed also pointing out the hour, but others fulfilling functions unlooked for, but carried out with action no less perfect.
And we find among many of these mechanisms curious similarities, in which a particular gear or spring is widely shared, though sometimes differently configured and sometimes even differing in function.
And in the earth we find the rusted remains of still others: some simple, others complex, but all sharing some part of their mechanisms with their contemporaries, and others both ancient and modern. Each is formed so as to function in some way, whether plain or subtle. We find moreover the least ancient to be most similar to the new and still functioning, and those nearby to be more alike with the rusty nearby, and-- by report-- those far away to have their own similar ancient relatives.
And when we again turn our attention to the first watch, now with mind
altered by seeing the breadth and diversity of the mechanical world, we see
more than we did at first: our eye drawn to certain gears and parts familiar
from one or another of those other devices, yet seeming disconnected and now
And finally-- most curious of all-- we conclude that these glittering
mechanisms do not arise ready-made from some designer's bench, but develop and change, beginning simply and similarly but diverging in
form until they reach the function we see today, however alike or different,
and whether simple or complex. How amazing is the ever-increasing diversity
of all this mechanical universe!
These are the very features found in the living world, and which are nicely explained only by evolutionary theory:
1. the diversity, yet order in living things (since they are related by common descent),
2. homology of structure-- especially that which is not related to function (forelimbs of whales, people, horses, bats and birds share ancestral arrangement of bones, even thought that arrangement has been bent to uses as varied as swimming, running, tool-use, and flying);
3. structures evolved for one purpose have been repurposed for new uses; structures that seem "irreducibly complex," such as the eye, are present in many simpler but still useful forms in other animals--showing that appearances can be deceiving.
4. a fossil record in which species appear and disappear through time in an orderly fashion;
5. extinct creatures related to still-living species in the same geographical places;
6. "vestigial" structures inherited from extinct ancestors (whale hip bones, for example) which seem no longer serve a purpose.
Of course, these are the features that were within reach of Darwin and, to some extent, Paley. Today there are others that were unknown to them:
1. genetics (we understand inheritance, and where the variation that is evolution's raw material comes from--something Darwin was quite confused about)
2. molecular biology, which allows us to compare genes and see the built-in molecular fossils that we all carry in our cells (some of my favorites: practically every living thing "reads" the language of DNA the same way, all use the same energy molecule, ATP, all build and use left-handed amino acids and right-handed sugars); and
3. a growing appreciation of living diversity and biological toughness that Darwin never dreamed of: bacteria living at the edge of space, inside rocks miles underground, and sealed into underground crystals for thousands of years.