Lawful patterns in an orderless universe
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- Reutlinger, A. Metascience (2012) 21: 653. doi:10.1007/s11016-011-9615-4
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In his new book, Joe Rosen, a theoretical physicist, sets out to determine the limits of scientific knowledge. His primary focus lies on the limits of knowledge in physics. Rosen understands his project as “a complement for, even an antidote to, books that create the misimpression that science can explain everything” (xi). Most importantly and contrary to what proponents of a “theory of everything” suggest, Rosen argues for the claim that the “universe as a whole” cannot be a proper subject of scientific research because it is intrinsically orderless and lawless. However, Rosen does not deny that science discovers lawful patterns (and explains the existence of some of them by more fundamental theories). Accordingly, Rosen’s guiding question is: “How can there be both order and law within the lawless universe?” (xi). Although the book is devoted to a philosophical topic, it should be emphasized that Rosen does not intend to address an audience of professional philosophers. Rather, his intended audience is physicists who are interested in philosophical and methodological questions regarding their own subject.
Rosen divides the book into eight chapters. My overview of these chapters will mainly focus on Rosen’s answer to his question how there can be laws in a universe that is—as a whole—lawless.
In Chapter 1, Rosen introduces several distinctions in order to set the stage for the arguments in later chapters. He distinguishes objectively and subjectively existing entities—the former exist mind-independently, while the latter exist mind-dependently. Relying on this distinction, Rosen introduces three kinds of facts in virtue of which a proposition can be true or false: (a) a proposition is objectively true if it is true in virtue of a mind-independent fact (e.g., “people normally fall to the Earth when the jump of a roof” is regarded as an objective truth, 15), (b) a proposition is subjectively true if it is true in virtue of a mind-dependent fact (e.g., “I felt sad last night”, 16), and (c) a proposition is logically true if it is true in virtue of definition, logically valid inference, etc. Rosen restricts his focus to objectively existing entities and objective truth because he believes that this is what physics aims to discover: “If the objective world is to be dealt with in a meaningful way, it must be dealt with objectively. The most nearly objective method we have for comprehending the real world is science” (24).
Chapter 2 lays out Rosen’s explication of what science is: “Science is our attempt to understand objectively the reproducible and predictable aspects of nature” (30). Rosen, as many other philosophers of science, assigns a high methodological value to reproducibility of experimental results, i.e., good evidence has to be gained by repeating reliable experiments (see pp. 32–36 for a detailed characterization of reproducibility). A law statement is, according to Rosen, intimately tied to reproducible experiments: “In our effort to understand (the natural world), we first search for order among the reproducible phenomena in nature, and then attempt to formulate laws that fit the collected data. Such laws […] condense all existing data […] into compact expressions. Thus, they are abstractions from the data from which they are derived, and unifying, descriptive devices for their relevant class of natural phenomena” (40). Rosen provides an illustration of this claim by a case study of Kepler’s laws of planetary motion (40–42). On the one hand, Rosen’s account of laws is a version of regularity theories of laws (such as the Mill-Ramsey-Lewis approach) because law statements are typically mere description of regular patterns. Rosen’s laws do not govern the world in any non-metaphorical sense. On the other hand, Rosen’s view of natural laws departs from the standard regularity approaches because the law statements summarize only the regularities revealed in very special circumstances (as we shall see in the reconstruction of Chapter 6, the special circumstances are the “quasi-isolated systems” in an experimental set-up).
In Chapter 3, Rosen observes that physicists are often not satisfied with knowing, e.g., the laws of planetary motion as “descriptive devises” that summarize the data of planetary motion. Instead, physicists demand an explanation of why these laws hold. Rosen suggests that such an explanation is given by theories—in the case at hand by classical mechanics. However, Rosen seems not to be aware of a problem. Although some laws might be explained by a more fundamental theory, it is at least not guaranteed that the laws of the fundamental theory can be explained by an even more fundamental theory. Hence, the distinction between description and explanation might not be as exclusive as Rosen thinks it is, because either one ends up with unexplained fundamental laws or one has to admit that—if the explanation of a law is indeed possible—it is the laws of the more fundamental theory which do the main explanatory work. However, let us ignore this problem for the time being. Rosen argues that if such an explanation of laws by a more fundamental theory is possible, then one realizes that the explanatory theory satisfies the well-known Kuhnian values of theory choice (46–54).
Chapter 4 reflects what has been accomplished up to this point from a meta-level. According to Chapter 2, scientists focus on finding lawful patterns in reproducible data. Rosen argues that his own project of asking questions such as “what is a law?”, “does science gather objective rather than subjective knowledge?” steps outside of the domain of physics. Instead of doing physics, one is engaged in philosophical research—“metaphysics”, as Rosen puts it (59). Metaphysics, for him, is the “philosophical framework in which science operates. In this sense, metaphysics is concerned with what lies around, below, above, before, and beyond science” (59). This is in line with a fairly standard view that metaphysics deals with highly generic (or meta-questions) as compared to physics. Surprisingly, Rosen entertains the view that metaphysics is a rather speculative enterprise when he states that “metaphysical considerations are unimpeded by any burden of obligation to be objectively true” and “personal taste and preference reign supreme in metaphysics, whereas in science, their influence, though present, is not of overwhelming importance” (61). This is an unnecessarily weak view of metaphysics, and it is not reflected by what Rosen actually does in his book as a metaphysician.
In Chapter 5, Rosen presents his central argument for the claim that scientific knowledge cannot encompass the universe as a whole. His argument runs as follows: if something is to be investigated by science, then it has to be a lawful pattern resulting from reproducible experiments. Yet, “the universe as a whole is a unique phenomenon and as such is intrinsically irreproducible” (72). Therefore, the universe as a whole is not the kind of object that can be investigated by science. Rosen presents several case studies from quantum mechanics and cosmology (72–81) which, according to Rosen, mistakenly understood as providing a theory of the universe as a whole. He argues for an alternative interpretation of these theories: they should be interpreted as metaphysical theories, not as theories of physics about objective reality.
Chapter 6 continues the line of argument originating in Chapter 5. Rosen wonders how there can be laws in a universe that is—as a whole—“intrinsically irreproducible”. This is a puzzling fact if one follows Rosen by assuming that laws are mere summaries of the data resulting from repeated reproducible, reliable experiments. Rosen’s response to this puzzle is that we should reject the idea that lawhood is an entirely objective matter. Instead, the truth-makers of law statement are the data generated by performing experiments with quasi-isolated systems. According to Rosen, a quasi-isolated system is a material system that is as nearly isolated as possible from the rest of the universe, i.e., whose interaction with the rest of the universe is reduced to the minimum possible (167). The philosophically initiated reader will recognize strong similarities to Nancy Cartwright’s nomological machines. As I mentioned above, Rosen’s claim that to be a law is relative to a reproducible experiment deviates from standard regularity accounts of laws of nature.
Chapter 7 contains a critical discussion of explanations of laws that rely on the anthropic principle. In Chapter 8, Rosen advocates a broad version of scientific realism. He emphasized that one should be aware of the fact that reality will remain “partially hidden” to science, because science is able to acquire knowledge only under the condition that researchers can perform reproducible experiments which generate data revealing lawful patterns.
Overall, Joe Rosen’s book is an ambitious and easily accessible philosophical reflection of physics by a theoretical physicist. As noted above, he presents an interesting regularity account of laws which diverges from standard regularity theories (such as the Mill-Ramsey-Lewis account), because lawhood is relativized to quasi-isolated systems in experiments. Moreover, Rosen achieves to make various interesting points (many of which I could not mention in this review), e.g., concerning the time-reversal invariance of laws (104–105) and the impact of quasi-isolated on the metaphysics of space and time (134–137). Further, Rosen uses the concept of quasi-isolated system, which he attributes to Ernst Mach (100, 106–111), in order to elucidate the content of inertial laws in Newtonian mechanics (99–102) and of laws describing the temporal evolution physical systems (102–106).