Summary of Sean Carroll’s “Purpose, Freedom, and the Laws of Nature”
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Sean Carroll (1966-) is an American theoretical physicist who specializes in quantum mechanics, cosmology, and the philosophy of science. He is the Homewood Professor of Natural Philosophy at Johns Hopkins University. He was formerly a research professor at the Walter Burke Institute for Theoretical Physics at the California Institute of Technology department of physics. He also is currently an external professor at the Santa Fe Institute.
Carroll’s essay “Purpose, Freedom, and the Laws of Nature” appears in Neuroexistentialism: meaning, morals, & purpose in the age of neuroscience, edited by Gregg Caruso and Owen Flanagan. I have found his article to be the best one I’ve ever read about the implications of modern physics for the existential issues of freedom and meaning. Here is a brief summary.
Carroll begins by noting the obvious connection between existentialism—which is primarily concerned with freedom and meaning—and sciences like biology and neuroscience. But Carroll is quick to point out that physics and cosmology are also relevant. For instance, quantum mechanics surely has something to tell us about human behavior and cosmology is important for understanding meaning and purpose. The purpose of the essay, Carroll writes, is to explain how “physics and cosmology have an impact on the foundations of both neuroscience and existentialism.”
1. Patterns and Determinism
Carroll starts by describing the change brought about by classical Newtonian mechanics. First, the idea of conservation of momentum: “every object in a state of uniform motion continue in that state unless acted upon by an external force.” This contrasts with Aristotle’s view that the natural state of things is to be at rest. Therefore while Aristotle’s world is one of causes and teleology (things are goal-oriented), in Newton’s world things just keep moving without any goal. This change in perspective calls into question the idea of purpose in human lives.
Second is the principle of conservation of information: if we knew the position and momentum of every particle and had infinite calculational ability we could predict the future and retrodict the past. The idea that the universe operates like a giant clock erodes belief in cosmic purpose. “If we are physical beings, obeying impersonal laws of nature … it’s not hard to conclude that life itself is purposeless.”
Carroll concludes this section by explaining how chaos theory does not undermine determinism. Chaos theory states that “small deviations between two possible states at one moment in time can develop into large deviations at later times.” Note how this is completely compatible with determinism. Chaos theory reminds us that we don’t have all the information necessary to predict the future, not that the future isn’t predictable in principle.
2. Quantum Mechanics
QM threatens classical determinism; it seems the best we can do when observing at the quantum levels is to predict probabilistically not definitively. Questions immediately arise. Is the universe fundamentally nondeterministic? Does this leave room for human freedom? Does observation imply that consciousness or human agency is of paramount importance?
The question of whether QM “is deterministic or not is up for debate.” Some theories (hidden-variable and many-worlds) maintain that the underlying physics is still deterministic, while others such as “dynamical collapse” disagree. The issue of human freedom remains unaffected. Nothing about QM implies “that human volition brings reality into being by the act of observation.” In fact, “consciousness plays no role in quantume mechanics.” QM is very different from classsical mechanics it doesn’t mcuh change our thinking about human agency and freedom
3. The Arrow Of Time
Time’s arrow refers to “the fact that the past and the future seem like very different things.” Yet none “of these features is inherent in the underlying laws of physics whcih treat the past and future on equal footing.” Carroll’s explanation of this discrpency entails an understanding of abstract physics but, to summarize, the “distinction between past and future arises from special conditions near the beginning of the universe.” The state of the universe has been evolving from a low entropy state at its beginning to one of higher entropy as it evolves.
4. Emergence
So the arrow of time is a true feature of our universe not found in fundamental physics. Levels above the fundamental microscopic level are said to be emergent. The idea is that we hav some system (a person, a box of gas) that can be describe as a bunch of atom at the microscopic level but described in simpler terms at the microscopic level. If we’re talking about weak emergence we refer to our using a macroscopic language about something that, with enough information and processing power, we could just as well describe using the microscopic language. Strong emergence is when “somthing truly new manifests at the macroscopic level, in behavior that cannot even in principle be described by microscopic consituents and fundamental laws.” The problem, states Carroll “is that there is no good evidence it [strong emergence] ever occurs in nature.”
Still weak emergence is enough to invoke different ontological concepts. At one level we may be particles and waves but at another level we can talk of values, consciousness, and decision making. Even are these emergent properties aren’t truly new; they are effectively new.
5. Existential Implications
How then do existential worries about freedom and meaning comport with modern physics and cosmology? After all, “There is little doubt that modern science has thoroughly undermined any hopes for a higher purpose or meaning inherent in the universe itself.” Moreover, there isn’t anything special about our constituative components. So existentialist generally claim we must accept absurdity and freely choose to make our own meaning while modern science “seems to reaffirm the absurdity while denying the freedom”
Carroll responds that while freedom and meaning have no place in the microscopic world they do have a place in the macroscopic. So the concept of choice is compatible with our macroscopic information about someone. When we say that we are free to the extent that we have “the ability to have acted otherwise” we aren’t referring to the microscopic quantum world where we can predict with a high degree of probabiltiy. There the idea of freedom isn’t useful. However at the macroscopic level then people can act otherwise; they can choose differently. Consider “that it is impossible to talk coherently about human beings without using a vocabulary of actions defined by choices.”
Similarly with purpose and meaning. They aren’t found in the fundamental laws of physics but they are useful in describing the macroscopic world we live in. Particles don’t have meaning, but we can; the universe doesn’t have meaning, but we can create meaning. As Carroll concludes, “What we bring to the world remains up to us.”
