PHYSICS HAS NO MONOGAMOUS DUCKS or polyamorous bonobos, so it must find moral order elsewhere. Fortunately, it has the entire rest of the universe in which to do so. The idea that modern (that is, post-Newtonian) physics and astronomy could provide moral, social, or political guidance was fairly common, if never quite as vigorous as the equivalent in the life sciences. By the early twentieth century, however, the physicists began to change their version of the “naturalistic fallacy.” It gradually became standard to incorporate aspects of the biological and social sciences when trying to yoke human behavior to physics or astronomy. And by the end of the twentieth century, this sort of reasoning mutated even further into an almost complete inversion of the traditional naturalistic fallacy. Instead of moving from “is” to “ought,” some physicists argued that the universe demonstrated how “ought” led to “is.”

The clearest example of this strange state of affairs is the anthropic principle (AP). Starting in the late twentieth century and continuing to the present, some cosmologists argue about whether there is a peculiar (or perhaps suspicious) “fine-tuning” of the universe for human life. For example, the values of several physical constants must be precisely what they are in order for stars and planets to form. It seems that the familiar features of our universe, such as carbon-based life, could exist only in a universe where these constants fall into a vanishingly narrow range. The conclusion is that if the properties of the universe were infinitesimally different, humans (or life in general) could not exist. The coincidence of all these numbers being exactly what they need to be, then, demands some comment or explanation.

The principle seems tailor-made for arguments along the lines of the naturalistic fallacy—but its proponents rarely take the opportunity. Instead, they use a distinctly different approach to prescribing human behavior. The social reasoning provided by the anthropic principle is quite distant from the moral order originally offered by physics. The peculiar aspects of these prescriptions perhaps help us understand why the physical sciences took a different trajectory than the life sciences vis-à-vis naturalistic reasoning.

THE MORAL AUTHORITY OF THE COSMOS

Cosmologists invoke the AP to make sense of the apparent fine-tuning of the universe. The AP comes in several varieties. The “weak” anthropic principle (WAP) simply notes that our presence as observers in the universe tells us that certain things about the universe are true. In particular, it says that there must be places in the universe where carbon-based life can evolve and that the universe must be old enough for it to have done so. This is essentially a statement of an elaborate self-selection effect. Our existence demands that planets exist, that some stars be old enough to have created carbon via nucleosynthesis, and so forth. The WAP is descriptive, not explanatory, and makes no claims beyond a general sense that life depends on some physical parameters. It is no more controversial than saying that because you are driving a car, cars must have been invented and manufactured. Given our interest here in the naturalistic fallacy, it is most appropriate to focus on the “strong” anthropic principle (SAP), which states that, as John Barrow and Frank Tipler put it, “the Universe must have those properties which allow life to develop within it at some stage in its history.”¹ This suggests a deep and profound connection between human life and the physical structure of the cosmos. Indeed, it claims that we (or some beings much like us) are the purpose of the universe. The fine-tuning of physics to make life possible is not a coincidence but is instead evidence for teleological design of the laws of nature. We are meant to be here.

We might expect such a conclusion to paint the universe as a font of social, ethical, or moral guidance. After all, if the cosmos was designed for our emergence, surely it has further lessons about how we should act, how we should treat each other, or what it means to be human. It is not difficult to imagine such a lesson: the philosopher Errol Harris argues that the SAP shows that life is the purpose of the cosmos. Therefore nuclear war or ecological disaster “is threatening to frustrate the cosmic purpose.” Accordingly, humans should behave such that “the course of history would reinforce the Anthropic Principle.”² The ratio of the electromagnetic and gravitational constants calls for world peace—and possibly recycling.

There is a long tradition of this sort of move—using physics and astronomy to reveal moral or social lessons hidden in nature. A classic example of moving from “is” to “ought” in physics is the application of Newtonian ideas to eighteenth-century political thought. J. T. Desaguliers produced a particularly clear instance of this with his allegorical poem The Newtonian System of the World, the Best Model of Government (1728). Written to celebrate the ascendance of George and Caroline to the throne, the poem explained how the dynamics of the solar system showed why the English political system was so impressive. The English king, limited by constitutional rule, was the Sun, and gravitational attraction should be understood as love of the monarch:

Historians of Victorian physical science have found several intriguing episodes in which political and social reform was justified by reference to nature. In the nineteenth century both astronomy and physics began moving toward a cosmological picture of change and directionality, which was often read as showing the need for “progress” in the human realm as well.

Simon Schaffer has documented how British political discourse invoked the nebular theory (the idea that the solar system formed gradually from a primordial cloud of gas and dust) in just this way. The development of nebulae into stars and planets solely under the influence of natural laws seemed a persuasive model for political and economic reform. If clouds could become stars, perhaps stagnant economies could become liberal ones? Schaffer tells us that the Scottish political economist and astronomer J. P. Nichol “publicly connected the processes visible in the history of the universe with the immediate fate of humanity.” The nebular theory was a particularly rich resource for this because it allowed for both change and law-like order, reassuring those who worried that calls for progress would lead to social chaos. The apparent inevitability of nebular transformation also promised the inevitability of reform. These moves were complicated by the uncertain status of the truth of the nebular theory throughout the century. The theory depended on whether astronomers had seen “true nebulosity,” a thorny question highly contingent on techniques of telescopic observation and visual inscription. Debates over the cloudiness of Orion's belt thus carried significant political stakes as well.⁶ (See Figure 1.)

The assertion by the second law of thermodynamics that entropy would always increase provided another model for universal progress. William Thomson (later Lord Kelvin) celebrated that “everything in the material world is progressive.” Crosbie Smith and Norton Wise's biography of Thomson shows how this progressive character of the universe supported his commitment to latitudinarianism in religion, Liberal Unionism in politics, and reform in science. To him, the second law announced that humans had a duty to aid in moral and industrial progress.⁷

Many of the Victorians justified these moves via their belief in a benevolent Creator deity. They knew that God had created the universe for them, so it was reasonable to find hidden advice from that deity. The particulars of design always carried a message. The SAP embraces just such a sense of design and seems an obvious foundation on which to build moral or social claims.

ONE STEP REMOVED

Strangely, few proponents of the SAP do this. There is much discussion among cosmological commentators of how the SAP elevates humanity to cosmic importance and how it changes the way we think about our relationship with the universe. It might even reveal that the cosmos is “melioristic.”⁸ But there is surprisingly little advice on how to live our lives.

Those anthropic commentators who do want to give social prescriptions often do so indirectly. That is, instead of drawing on the actual physics of the AP, they take a detour through other disciplines (typically the life and social sciences). The philosopher John Caiazza's book on the AP, The Ethics of Cosmology, aimed to find the “humanistic consequences” of cosmology. But after a general survey of the AP, the details of cosmology disappeared. When he argued for “Cosmic Family Planning” he actually referenced biology, and for the “Cosmic Evolution of the State” his examples came from political history.⁹ Intermediate disciplines have become necessary to connect physics and astronomy to daily life. The physical sciences by themselves no longer seem adequate to support the kinds of claims that Nichol or Thomson wanted.

This subtle but important shift was well under way by the interwar period. The writings of the British astronomer A. S. Eddington argued that relativity and quantum physics revealed that the universe was idealistic rather than materialistic. This discovery, he contended, made it impossible for political systems such as Marxism to model themselves on a materialistic view of nature—a fairly typical example of guidance from physics (though Eddington rejected design arguments per se).¹⁰

However, it is interesting that much of the criticism Eddington received was aimed at his willingness to leap directly from physical science to human activity, without considering that the life, mind, and social sciences might have important things to say on the subject. It seems likely that the increasing authority and autonomy of those disciplines made it less tenable for physical scientists to make social pronouncements solely from their own results. When such scientists did seek to provide moral or political guidance, it became standard to append a discussion of biology or sociology to bridge their work to their end goals.

Consider the astronomer Harlow Shapley, who suggested in 1963 that since the stars were “supranational” and developed over time, humans should also aspire to those goals.¹¹ The evolution of the cosmos meant that nations should avoid wars and strive for cooperation. However, Shapley did not move directly from the stars to the United Nations. Instead he took the reader on a detour through human sense receptors and entomology, establishing the continuity of principles that justified him in bringing his expertise to bear on educational policy and international cooperation.

Shapley also provided an example of an interesting (and common) tangent to the naturalistic fallacy, where the argument was less “We should behave as nature does” and more “We should behave as scientists do.” He asserted that astronomers already acted in a fully international mode and suggested that the rest of the world ought to follow their lead.¹² This claim was often mixed in with his earlier arguments, though, which made it easy for the reader to conflate the moral lessons of astronomy with the moral lessons of astronomers. Whether this is intentional on Shapley's part is unclear, but it certainly gave his position further support even while muddying the conceptual waters.

Life sciences are not the only available bridge, of course. With the SAP, religion is often deployed as an intermediate step. Arthur Peacocke, the chemist turned theologian, tells us that the AP will force us to rethink our image of the Creator.¹³ What to do after that is unclear—he implies that the reader possesses some existing set of tools through which she will relate to her Creator. Neither Peacocke nor the AP more generally offers any specific religious guidance. Even discussions of Big Bang cosmologies follow the same pattern. It quickly became standard to say that the Big Bang proved the existence of a Creator. But few people took the next step and declared that the Big Bang meant that everyone should start taking Communion. The results of the science were used to make a general point (that God exists or that free will does not), and then what social or ethical guidance ought to be followed was left as an exercise for the reader. This move is essentially the descriptive/prescriptive distinction common to Weberian self-descriptions of the social sciences—the proper role of scientists was simply to describe, not instruct. Physicists' interest in replicating this framework again suggests their increasing willingness to recognize the territorial claims of those disciplines.

THE INVERTED NATURALISTIC FALLACY

But even with these bridging techniques, the SAP has not produced a robust body of claims that we would recognize as part of the naturalistic fallacy. Instead, the AP typically gives rise to a very distinct kind of discussion. The usual formulation of the naturalistic fallacy links “is” and “ought.” The SAP is, at its core, a claim about the “ought” of the universe: the universe ought to bring life into existence. Specifically, the SAP is about whether it is inevitable that life appear. It is a statement that the characteristics of life in the universe could not have been otherwise. This means that, in the framework of the SAP, everything has to be exactly as it is.

This creates a peculiar way of talking about human activity. The physicists John Barrow and Frank Tipler, in their classic book on the AP, note that the SAP implies that intelligent beings play “some essential role in the Cosmos.” But these beings could not fulfill this role if confined to one planet, owing to the finite lifetimes of stars and habitable planets. Intelligent species will therefore “necessarily” develop the technology for interstellar travel.¹⁴ This is not an invocation to action. Barrow and Tipler are not warning their readers that the SAP demands that humans choose to act in a particular way. Rather, they are saying that the SAP means that humans will act in a particular way. There is no choice: ought simply is.

Barrow and Tipler's discussion of the long-term colonization of the galaxy takes a similar approach. Such colonization, they say, will happen via Von Neumann probes (self-replicating machines, here abbreviated “VN probes”). Again, they do not advocate for the construction of such probes; they simply declare that all intelligent species will construct them. Once the probes are constructed, colonization will transpire exactly according to the mathematics of population expansion (which Barrow and Tipler say are confirmed as true by the scramble for Africa and the occupation of the Oklahoma Territory). This reasoning leads to the conclusion that our galaxy will be completely colonized within the first billion years after any intelligent life appeared. The authors explicitly reject any arguments that a civilization might choose not to build VN probes or choose not to expand in this way. In a kind of reverse naturalistic fallacy, they even argue that the antiracist trends of modern society clearly demonstrate that VN probes, as pseudo-intelligent entities, will be given full rights to reproduce without restriction.¹⁵ The future actions of human societies are not a matter of decision or intent but, instead, the result of deep-seated features of the cosmos.

This resolution of the classical Greek tension between nature and human agency (see Brooke Holmes's essay in this Focus section) is perhaps distinctive to cosmology. It may be that cosmology, as a discipline, does not leave much room for choice. Its equations are largely deterministic and continuous. There is little space for the choice of intelligent beings to influence the grand scheme of the universe one way or another. From the cosmological point of view of the AP, life and intelligence are inevitable parts of those deterministic equations. And in the SAP, all the properties of the universe were carefully planned for a particular purpose. So the question of whether humans choose to act in accordance with this plan is nonsensical. Humans are merely a particularly well-dressed part of the universe; they will fulfill the cosmic plan regardless. The naturalistic fallacy in some sense was never even an opportunity.

CONCLUSION

When the occasional attempt to base society directly on physics appears today, it is rarely taken seriously as a point of discussion. In September 2013 Chibuihem Stanley Amalaha, a chemical engineering student in Lagos, announced that he had used elementary magnetism to prove that same-sex marriage is wrong.¹⁶ He was roundly mocked in the mainstream media, and the Internet enjoyed several days of fun at his expense. If he had been a neuroscience student presenting fMRI images, or a primatologist discussing adoption behavior, his results would have been seen as legitimate provocations to conversation. His ideas might not have commanded assent, and he would still have been attacked—but perhaps he would not have been dismissed so completely and instantly. It seems self-evident today that magnetism and marriage have nothing to do with one another. In this era of the Human Genome Project and behavioral economics, a great deal of work would be necessary to make that leap.

The naturalistic fallacy, then, has had a rapidly decreasing presence in the physical sciences. After the professionalization of the life and social sciences, such matters were generally seen as alien territory. That is not to say that no one deployed physics and astronomy for political purposes. Rather, the common move was to remove the social and ethical reasoning one step from the science. Physicists were not disinclined to make suggestions; they just required other resources to do so.

Finding clear examples in physics of reasoning similar to the naturalistic fallacy is sometimes difficult. Often this is caused by obfuscating bridging moves, such as those made by Shapley. More commonly the problem is one of directionality. Should we say that Thomson's interest in political progress came before his interest in cosmological progress? Or the other way around? Or that the two were intertwined? The classical formulation of the naturalistic fallacy assumes a stable understanding of nature that is then exported to humanity. But scholarship in the history of science has shown that achieving such a stable understanding is often quite difficult and is often deeply entangled with exactly the sort of social and political issues that are supposed to be the end result. A characteristically confusing situation can be found among the subjects of David Kaiser's How the Hippies Saved Physics. Fritjof Capra worked to persuade his readers that quantum physics was teaching us to live holistically, and Fred Alan Wolf created a quantum-justified self-help movement—apparently clear examples of the naturalistic fallacy.¹⁷ But who can say for certain whether these figures became interested in quantum physics in the first place because of its supposedly holistic implications, or whether they developed their holistic interpretation after having learned some quantum theory as students? Cart/horse confusion can make these assessments challenging.

Finally, there may also be deep conceptual issues that make physics less fertile than the life sciences for naturalistic reasoning about human behavior. The example of the anthropic principle shows us that, in some sense, the basic assumptions of the physical sciences became incompatible with the basic assumptions of the naturalistic fallacy. Physics and astronomy still assume (putting aside quantum mechanics for the moment) that the macroscopic universe is predictable in principle. The idea of a choice to act a particular way, then, makes little sense. Events are caused owing to the properties of the universe, regardless of what we want. If the ratio of the electromagnetic and gravitational forces has a lesson for monogamy, it will not be one we can choose to follow. We will simply be carried along with it, like the clouds of a collapsing nebula.