… Today the argument isn’t over which gods exist but over whether any god exists; or even whether anything you could call a higher purpose exists. Still, if Muhammad’s argument doesn’t work today, the kind of argument he made is, more than ever, the kind of argument that has to be made if people are to be persuaded: an argument that evidence of divine purpose—[What Muhammad called] the “signs”—are embedded in the natural world; an empirical argument.

The conventional wisdom is that such arguments are either intrinsically illegitimate or unfailingly ineffectual. In fact, there’s a standard historical anecdote that is trotted out to show how hopeless they are. The funny thing is that this anecdote, when closely examined, shows something quite different.

The anecdote is the story of the “blind watchmaker.” It involves William Paley, a British theologian who wrote a book called Natural Theology in 1802, a few years before Darwin was born. In it he tried to use living creatures as evidence for the existence of a designer. If you’re walking across a field and you find a pocket watch, Paley said, you know immediately that it’s in a different category from the rocks lying around it. Unlike them, it is manifestly a product of design, featuring a complex functionality that doesn’t just happen by accident. Well, he continued, organisms are like pocket watches: they’re too complexly functional to just happen by accident. So organisms must have a designer—namely, God.

Thanks to Darwin, we now know that Paley was wrong. We can explain the complex functionality of organisms without positing a god. The explanation is natural selection.

Darwinians who are atheists have been known to celebrate the failure of Paley’s explanation. They love to note how futile this attempt to empirically argue for the existence of God turned out to be. What they tend not to emphasize is that Paley was half right. The complex functionality of an organism does demand a special kind of explanation. It seems pretty clear that hearts are in some sense here in order to pump blood, that digestive systems are here in order to digest food, that brains are here in order to (among other things) help organisms find food to digest. Rocks, in contrast, don’t seem to be here in order to do anything. The kinds of forces that created a rock just don’t seem likely to be the kinds of forces that would create an organism. It takes a special kind of force to do that—a force like natural selection.

Indeed, so special is natural selection that lots of biologists are willing to talk about it designing organisms. (Or, actually, “designing” organisms; they tend to put the word in quotes, lest you think they mean a conscious, foresightful designer.) Even the famously atheist Darwinian philosopher Daniel Dennett uses that kind of terminology; he says this process of “design” imbues organisms with “goals” and “purposes.” For example: organisms are “designed” ultimately to maximize genetic proliferation, and are thus “designed” to pursue goals subordinate to that ultimate goal, such as finding mates, ingesting nutrients, and pumping blood.

The take-home lesson is simple. It is indeed legitimate to do what Paley did: inspect a physical system for evidence that it was imbued with goals, with purpose, by some higher-order creative process. If the evidence strongly suggests such a thing, that doesn’t mean the imbuer was a designer in the sense of a conscious being; in the case Paley focused on, it turned out not to be. Still, the point is that you can look at a system and argue empirically about whether it has, in some sense, a “higher” purpose. There are hallmarks of purpose, and some physical systems have them.

Well, the entire process of life on Earth, the entire evolving ecosystem—from the birth of bacteria through the advent of human beings through the advent of cultural evolution, through the human history driven by that evolution—is a physical system. So in principle we could ask the same question about it that we asked about organisms; it could turn out that there is strong evidence of imbued purpose, as Paley and Dennett agree there is in organisms. In other words, maybe natural selection is an algorithm that is in some sense designed to get life to a point where it can do something—fulfill its goal, its purpose.

And, actually, when you think about it, some of the evidence you might point to as the hallmark of purpose in organisms has analogues in the evolving ecosystem.

Here is some of the evidence in the case of the organism. A single fertilized egg cell replicates itself, and the offspring cells in turn replicate themselves, and so on. Eventually the resulting lineages of cells start evincing distinctive specialties; there are muscle cells that beget muscle cells, brain cells that beget brain cells. If Paley were around today to watch videos of this process, he would say, Wow!—look at how exquisitely directional this process is; the system grows in size and in functional differentiation until it becomes this large, complex, functionally integrated system: muscles, brains, lungs, and so on; this directional movement toward complex functional integration is evidence of design! And, in some sense of the word “design,” he would be right.

Now here is a somewhat parallel description of the history of the ecosystem on this planet. First, a few billion years ago, a single primitive cell divides. The resulting offspring cells in turn replicate themselves, and eventually different lineages of cells (that is, different species) emerge. Some of these lineages eventually become multicellular (jellyfish, birds) and evince distinctive specialties (floating, flying). One lineage—let’s call it Homo sapiens—is particularly good at thinking. It launches a whole new process of evolution, called cultural evolution, that spawns wheels and legal codes and microchips and so on. Humans use the fruits of cultural evolution to organize themselves on a larger and larger scale. As this social organization reaches the global level and features a richer and richer division of economic labor, the whole thing starts to resemble a giant organism. There’s even a kind of planetary nervous system, made of fiber optics and other stuff, connecting the various human brains into big megabrains that try to solve problems. (And some of the problems are global—how to head off global warming and global epidemics, for example.)

Meanwhile, as the human species is becoming a global brain, gradually assuming conscious stewardship of the planet, other species—also descended from that single primitive cell that lived billions of years ago—perform other planetary functions. Trees are lungs, for example, generating oxygen.

In other words, if you watched evolution on this planet unfold from a distance (and on fast-forward), you would find it strikingly like watching the maturation of an organism: there would be directional movement toward functional integration. So why can’t the part of Paley’s argument that can be validly applied to an organism’s maturation—the idea that it suggests a designer of some sort—be applied to the whole system of life on Earth?

This is just a question, not a rigorous argument. To argue seriously that the system of life on Earth, the evolving ecosystem, is a product of design, or at least “design,” and thus in some sense imbued with higher purpose, or at least “higher” purpose, would take a whole book. This is not that book.

And even if you had successfully made that book-length argument, questions would remain. Was the purpose imbued by some conscious being or just by some unconscious process? And, in either event, is the purpose in some sense good? Good enough, at least, so that even if you couldn’t specify the exact nature of the designer, you would be tempted to characterize the purpose itself as, perhaps, divine?

This question, too, could encompass an entire book—and this book isn’t that book, either. Still, this book has shed light on a question that would certainly arise in the course of that book: Does human history by its nature move toward something you could call morally good?

That’s a question we’ll treat more fully in the next chapter.…