In his Summa Theologiae, Thomas Aquinas famously gave “five ways” by which God can be known through the power of human reason. Each of these five ways begins not with a conceptual analysis in the realm of ideas, but with empirical observation of some aspect of the natural world. The fifth of the five ways begins with what Thomas calls the “governance of things,” that is, the observed tendency of natural entities, beginning with the lowest inorganic entities, to act in an ordered manner. Thomas argued that this observed order is indicative of purpose in nature and ultimately of an Intelligence that purposefully orders the things of nature.
It will come as no surprise that many thinkers in recent times have rejected Thomas’ “fifth way,” along with his other four. Notably, the skeptics have rejected not only the conclusion of the argument (the existence of a governing Intelligence), but also its premise (that natural processes do, in fact, exhibit purpose). This essay discusses developments in modern science that provide persuasive grounds for the discernment of purpose in nature. It thereby serves as a “preface” to an argument such as the fifth way by giving renewed support to its premise.
From the evolution of galaxies to the development of the smallest flower, nature exhibits exquisitely intricate and complex patterns of order. Throughout history, humanity has been amazed and fascinated by these patterns. The progress of science has only deepened our awareness of the order of nature by extending our ability to observe natural phenomena and systematically describe their elegant harmony. Many scientists and philosophers of science see manifestations of purpose in the natural order, beginning with the laws that govern the smallest subatomic particles and reaching to the highest forms of conscious life.
Although the topic of purpose in nature is now considered controversial, such purpose was once widely recognized and affirmed by the most sophisticated and critical thinkers. The greatest of the Greek philosophers, from Plato and Aristotle to Plotinus, considered the evidence of purpose in nature to be compelling and clear. The Stoics, for example, spoke of a logos or “reason” that embodied order and purpose within the cosmos. In general, these philosophers were willing to reason boldly from an observed effect to an inferred cause, even when the cause hypothesized was not itself observable.
Their confidence in such reasoning grew out of their strong belief that nature is not only ordered, but that its order is fundamentally intelligible, so that it can be effectively understood by the human mind. The physical processes observed in nature were believed to be not only consistent but ultimately rational in character. Therefore, the human investigator, employing rational tools such as mathematics, should be able to uncover the secrets of these processes and allow their inner workings to be clearly grasped. The pervasive order and intelligibility of nature was further taken to exhibit purpose at various levels. The entities observed in nature act not only in a predictable and consistent manner but so as to integrate harmoniously into a larger whole.
However, since the Enlightenment, there has arisen a contrary strand of thought that is deeply suspicious of the idea of purpose. This philosophy, sometimes known as “positivism,” does not deny the order of the physical universe, but simply takes this order as a “brute fact” that stands in no need of further explanation. The order of nature may be rationally intelligible and explicable through the tools of science and mathematics, but for the positivist it makes no sense to ask “why” this is so. According to this perspective, the universe “just is” as we encounter it. The task of science is restricted to producing ever more complete and precise descriptions of empirical phenomena. However, inferences concerning unobserved theoretical entities and questions pertaining to “why” the world is as we observe it are both dismissed as “unscientific.” Positivism simply forbids one to ask why the laws of nature are those that we discover rather than some others.
Yet, the advances of physics in the past century have made the stance of positivism increasingly difficult to maintain. As physics has explored phenomena at ever smaller scales that are ever more difficult to detect, it has moved further and further away from the everyday experience of human beings. When working in regimes that cannot be easily observed, physics becomes increasingly reliant upon the human ability to reason from observed effects to unobserved causes. Through such reasoning, theoretical entities characterized by mathematical relations are often hypothesized to account for observed effects, even though the entities themselves have not been observed.
The early history of modern particle physics offers dramatic examples of such reasoning. For example, in 1930, Wolfgang Pauli sought to explain an anomaly associated with “nuclear beta decay” by postulating the existence of an undetected particle. In 1933, Enrico Fermi wrote a paper concerning the particle, which he called the neutrino, and submitted the paper to the journal Nature. From one point of view, Pauli and Fermi were reasoning straightforwardly from observed effect to an undetected cause. Yet, this mode of inference offended the canons of positivism, and so the editors of Nature rejected Fermi’s paper as too speculative and remote from reality. The neutrino remained unobserved until 1956, when it was detected using the Savannah River reactor.1
Just as the restrictions of positivism have proven untenable in regard to theoretical entities such as subatomic particles, so they appear questionable in regard to the discernment of purpose. The stimulus for the consideration of purpose lies in the nature of the scientific enterprise itself. Science seeks to identify the laws by which the natural processes of our universe evolve in time, and these very laws serve as indicators of purpose. The laws discovered by science have allowed the complex, multilayered order found in the universe to emerge over time from the relative homogeneity of the universe’s early state. These laws thus manifest an astounding creativity whose potential continues to unfold. It is the very operation of these laws that produces the subtle and amazing order of nature. Moreover, the order of our universe is closely calibrated to the particular laws that produce it. Physical laws chosen at random would, in an overwhelming majority of cases, lead to a universe completely lacking in the kind of order we observe. It therefore strains credibility to suggest that we ought simply to “take for granted” either the laws or their marvelous outcome.
A fundamental example of order in physical laws is found in the notion of symmetry.2 Symmetry is an intuitive concept familiar to us in the form of regular shapes, like that of the snowflake. However, symmetry can also be precisely characterized through the branch of mathematics known as group theory, which allows us to describe types and degrees of symmetry. A central discovery of modern physics has been the manner in which various laws exhibit particular mathematical symmetries. Furthermore, as physicists relate the various laws to each other, an important relationship emerges. As we move to physical laws at “deeper” or more fundamental levels of organization, we find higher degrees of symmetry. The phenomena at more “shallow” or easily observed levels of organization typically have lower degrees of symmetry. Yet, the higher degrees of symmetry found at the deeper levels of organization, while exhibiting an intricate order, are in no way logically necessary.
The pattern discovered in regard to symmetry holds true of the order in nature more generally. As the sources of order are analyzed in terms of physical laws at various levels of organization, order is never seen to emerge from a lack of order. Rather, the order at each observed level of organization is found to unfold from a greater order at a deeper level. Thus, the scientific process explains order by mathematically relating it to a more profound order. The deepest levels of order, such as those that may be revealed by a future theory of quantum gravity, are the least readily observed. As the scientific process advances, progressively greater degrees of order are exposed. From the perspective of twenty-first century physics, the universe appears far more intricately ordered and profoundly rational than it did to Plato or Aristotle.
What then is the significance of this order? To explore further the implications of natural order, we must begin to confront the very questions that positivism forbids us to ask. Why are the laws of physics what they are, rather than otherwise? These laws are surely not logically necessary, as are purely mathematical theorems. Even when physicists eventually arrive at a fundamental physical theory, such as a theory of quantum gravity, there is no reason to believe that this theory will be logically necessary. In other words, it will always be logically possible for the universe to have been otherwise. Physical laws that are not logically necessary may precisely describe order, but they do not “explain away” that order in any way that would obviate the question of purpose. Such laws possess no status that would prevent us from asking questions about their further significance. When such questions are squarely posed in regard to fundamental laws, with their intricate harmony and elegance, purpose seems to become manifest.
Moreover, the physical laws that have already been discovered seem to be “fine-tuned’ to produce a universe in a narrow regime that allows the emergence of novel structures through a process of self-organization. This self-organization is manifested first at the astrophysical level, in the structure of stars and galaxies, before we even consider the emergence of life. To permit such self-organization, the laws must achieve a delicate balance between an utterly chaotic and disorganized universe and one that is completely static and uninteresting. The fine-tuning of our physical laws to produce such an order weighs heavily against the credibility of treating those laws as “brute facts.” Rather, the fact that our universe appears to lie so perfectly in the favored range seems indicative of purpose.
The advocates of positivism sometimes object that the notion of purpose adds no “empirical content” to the known physical laws. However, this objection misconstrues the idea of purpose, treating it as if it were an extra force above and beyond those already accounted for. Purpose is not supposed to have empirical content apart from the physical laws in which it is manifest. On the contrary, it is the empirical content of the laws themselves that persuasively leads us to posit purpose.
Although the idea of purpose may not alter the empirical content of physical laws, it can nevertheless greatly affect our understanding of the significance of life and its relation to the rest of nature. Indeed, the evidence of the natural order suggests that one of its purposes lies in the appearance of life itself.
The astounding appearance of life in accordance with natural processes reveals the special character of those processes. One might imagine that the appearance of life was a kind of freak accident, an enormously improbable event that somehow nevertheless occurred. Analysis of the essential physical and chemical processes suggests that such is not the case. Rather, the appearance of life toward the end of the long process of cosmic organization appears to suggest that support for life is part of the universe’s purpose.
We can initially consider the laws of physics themselves. According to the so-called “anthropic principles,” the very possibility of life is highly dependent on the exact value of the constants that govern the fundamental forces of nature.3 If the values of the constants were to differ by even a few percent, life as we know it could not exist. This sensitivity of the constants can be interpreted as a sort of “fine-tuning” in support of life even at the level of fundamental physics.
Consideration of organic chemistry points in the same direction. When we examine the distribution throughout the universe of the carbon-based compounds that form the basic constituents of life, they are found to be sufficiently plentiful and widespread for life to arise in many places. While this fact does not show that life must arise or explain how it arose, it does at least establish that the basic conditions needed for life are not rare. If life were to be found elsewhere in the universe, it would provide further evidence of the propensity of the natural order to support life and thus reinforce the hypothesis of life as one purpose of that order.
Moving from organic chemistry to the next higher level, we come to biology proper. An important new perspective comes from viewing biology in the light of modern computational science, including the branch known as information theory. The cell, whether that of a single-cell or multiple-cell organism, can best be understood as a highly sophisticated system that carries out a variety of information processing tasks.
Moreover, there is a precise sense in which the cell can be considered to act as a “digital” rather than an “analog” computer. Analog computers are hard-wired to perform some particular task through the physical design of their hardware. They have no separate software to speak of. Digital computers, on the other hand, have separate hardware and software layers. Rather than carry out a particular task, the hardware layer is designed for the more general activity of processing information that is symbolically encoded. This more sophisticated arrangement allows for the tasks carried out by the system to be controlled by the software layer, rather than hard-wired into the system’s physical structure. In other words, the digital computer is essentially a processor of information.
In artificial digital computers, the software and data are ultimately represented in the form of binary digits. If we view the cell as a kind of natural digital computer, its software is encoded in its genes.4 Although the genes clearly depend on the underlying biochemistry of the cell for their “instructions” to be properly “executed,” the information that they encode is logically distinct from that biochemistry. The genetic “software” is encoded in the physical “hardware” of DNA and RNA, and yet that software is essentially informational rather than material. The independence of the genetic software from its biochemical hardware is perhaps best illustrated by the process of cell division, in which the software causes a whole new hardware unit to be replicated for itself. The information contained in the genetic software is fundamentally procedural, providing instructions to carry out a set of tasks in order to achieve particular goals at various biological levels. Such procedural information is essentially goal-oriented and thus purposeful.
Not only do genes encode a high degree of information from the perspective of information theory, but this information must be very specific in order to carry out the proper biological functions. One approach to understanding the genetic encoding of such complex information comes from the computational study of “genetic algorithms,” which are computational methods that incorporate the concept of natural selection.5 Genetic algorithms show that natural selection acts as a search method through a “space” of possible configurations. As a result, natural selection performs a kind of “information concentration” that allows a system locally to increase its information content by drawing energy from its global environment. In man-made genetic algorithms, the human designer supplies a mathematical “fitness function” by which potential solutions are evaluated. In contrast, the fitness function for an organic system is determined by its environment as shaped by natural laws. In either case, the fitness function implicitly establishes a goal for the process of natural selection. As noted in our discussion of symmetry and natural laws, the order observed at each level of natural organization is found to emerge from a greater order at a deeper level. The laws that shape the fitness function for organisms are deeper than the organisms themselves and so must contain a greater order that implicitly directs the goal-oriented process of natural selection.
The kinds of information processing manifested in the myriad forms of life in our world display an extraordinary sophistication. Even more remarkably, these forms of life now include rational beings capable of reflection upon that very world. Humanity systematically probes the natural order to determine the laws by which that order operates and perhaps discover its purpose. It is surely a profound attribute of nature that its laws support a development that eventually produced rational beings who turn their attention to the natural order and all that flows from it. This attribute of nature suggests that rational beings are themselves part of the purpose of the universe and, conversely, that part of the purpose of rational beings is to understand the workings of the universe. These twin purposes are mutually reflective and are characterized by a multifaceted interplay. If humanity finds its own purpose, in part, in seeking the purpose of the surrounding world, then we would expect science to play an integral part in the life of humanity, contributing deeply to the fulfillment of human purpose. Human beings are able to employ their rational powers to model the very processes operative within the human body and mind.
An integrated vision of the respective purposes of the universe and humanity must begin with the scientific study of nature, but the resulting evidence of purpose in nature is not a terminal point for human reflection. Rather, such an understanding prepares the way for an adequate consideration of a higher purpose, one that transcends the natural world, in a manner fully integrated with our advancing scientific knowledge. Too often, thinkers sympathetic to religion have attempted to secure a place for higher purpose by supplementing nature with a “God of the gaps,” whose assigned role is to account for phenomena for which a scientific explanation has yet to be found. Such an approach to God amounts to an “argument from ignorance” and is perhaps the weakest of all theistic arguments. The approach of Thomas Aquinas was very different. He took the principles of nature itself as his starting point and built upon them through philosophic analysis. There is tremendous scope for contemporary philosophers and theologians to pursue a similar path, moving from the scientific indications of purpose in nature toward a transcendent end in the manner of the fifth way.
1 Frederick Reines, “The Early Days of Experimental Neutrino Physics,” Science 203, no. 11 (1979).
2 Joe Rosen, Symmetry in Science: An Introduction to the General Theory (New York: Springer-Verlag, 1995).
3 John D. Barrow and Frank J. Tipler, The Anthropic Cosmological Principle (Oxford; New York: Oxford University Press, 1986).
4 John S. Mattick, “The Hidden Genetic Program of Complex Organisms,” Scientific American, October 2004, 60-67.
5 Melanie Mitchell, An Introduction to Genetic Algorithms (Cambridge, MA: The MIT Press, 1996).