Revisiting Reduction and Emergence in the Sciences

Many thanks to John Schwenkler for allowing me to blog here about my new book Reduction and Emergence in Science and Philosophy. The book is long, so I will seek to unpack the main themes of the book’s four sections in subsequent posts. At the end of this post, I have included a link to the book’s introductory chapter available at CUP’s website that surveys the contents of the book at greater length.

In this post let me sketch the rather different methodological approach I take . We presently find ourselves in the midst of a new cycle of scientific debates over ‘reduction’ and ‘emergence’,  or what Robert Laughlin (2005) terms a new ‘Battle of the Ages’, across bitter fights in physics over the supercollider or high-energy superconductors, biological debates over cells and their molecular components, disputes over neurons and neuronal populations, and many other concrete cases at various levels of the sciences.

Superficially, one might therefore think that very little has changed in the sciences. At the beginning of the last century, one of the great scientific disputes also raged between reductionists and emergentists of various kinds. However, closer inspection reveals important differences with these older debates whose central question was whether all natural phenomena are composed and, in particular, the chemical and biological entities whose composed status had, at that point, remained inscrutable for decades. Putting the issues in a different way, the earlier battles focused on whether all levels of nature, including chemical or biological phenomena, were amenable to what I shall term ‘compositional explanation’ — that is, to explanations of higher level entities built around lower level entities taken to compose them. Famously, however, during the course of the twentieth century the rise of quantum mechanics and molecular biology finally provided compositional explanations in chemical and biological cases. And such headline-making advances occurred against the backdrop of continuing waves of compositional explanation in the full range of other sciences. The earlier debates were consequently settled in the sciences, since these explanations provided qualitative accounts of the components of the entities found at many levels of nature, including chemical and biological phenomena.

As Laughlin notes, contemporary debates have been transformed through our improved understanding of the components of complex aggregations, or “collectives” to use Laughlin’s term, from high-energy superconductors, to eukaryotic cells, and on to slime mold, neural populations or eusocial insect colonies. Often using new techniques, for the first time we now also have quantitative accounts of the components found in such complex collectives. And these discoveries fuel our new cycle of debates. Thus contemporary scientific reductionists and emergentists each apparently endorse the ubiquity of compositional explanation and their disputes no longer concern the existence of composition at all levels in nature, but instead focus upon opposing accounts of its character and implications. The two sides thus clash over an array of diverging epochal ontological commitments implicitly assumed by either side in contrasting views of the very nature of composition (i.e. ‘parts’ and ‘wholes’), the form of the aggregation that always accompanies such composition, the varieties of determination we find in the universe, and the character of the fundamental laws, amongst a variety of other issues.

The latter scientific debates are dislocated, as many of the scientists engaged in them note, from philosophical discussions of, and frameworks for, reduction/emergence. It is obviously troubling to find theoretical differences between philosophical and scientific debates on such important topics. And it leaves us with a pressing question: Are philosophical or scientific approaches to reduction and emergence, as well as connected foundational issues such as the nature of scientific composition, more likely to be closer to the truth about the deeper issues and live positions of our times?

One of my main negative conclusions in the book is that the scientists are right to be wary, for I show at length that the received philosophical wisdom has gotten things wrong. On the positive side, I show that the scientific discussions have come closer to the truth.

Overall, my focus is therefore on the scientific debates and their underlying phenomena in compositional explanations and their concepts. I  start by re-engaging these key scientific phenomena. Initially, I provide better theoretical frameworks for scientific concepts of composition deployed in compositional explanations (and implicitly re-examine such explanations as well). I then use my theoretical account of scientific composition to engage, and reconstruct, the positions of the scientific reductionist, and the scientific emergentist, in turn. Using these reconstructions, I refresh our view of the state of the debate and its deeper issues.

Throughout the book, I therefore follow a three-step methodology. First, I pursue a descriptive project of articulating the features of a scientific concept or position. Then, second, using my descriptive account, I construct a theoretical framework for the concept or position that allows me to assess the arguments built upon the concept or position. But my work is thus not merely descriptive, although its initial phase does focus on articulating and theoretically reconstructing scientific concepts and positions. For, third, I then also prosecute the prescriptive project of assessing both philosophical, but also scientific, positions and arguments about scientific composition, reduction and emergence.

Using my better theoretical frameworks for scientific composition, reductionism and emergentism, I outline why the most widely endorsed views in philosophy and the sciences are not amongst the viable positions about the structure of cases of compositional explanation and nature itself. And I illuminate the false dichotomies philosophers have endorsed about both reduction and emergence. However, I also detail a number of places where both scientific reductionists and emergentists have made bad arguments. For example, I detail how the most common argument offered by scientific reductionist’s for their claim that “Wholes are nothing but their parts” is actually invalid. And, contrary to the claims of scientific emergentists, I outline why the existence of multiple realization, feedback loops, the indispensability of higher sciences, and/or the necessity of using non-linear dynamics or explanation by simulation, do not alone provide good arguments against scientific reductionism once it is properly understood.

Appreciating the flawed arguments recently offered in the sciences, and philosophy, I show that both sides in scientific debates, although each hitting on one of the live positions, have plausibly failed to appreciate the strongest opposing views. And I show that similar problems affect even those philosophers pursuing pioneering work on the scientific views. Given the comparative nature of scientific theory appraisal, where a theory is assessed by comparison to the strongest relevant rivals, I consequently show that extant defenses using empirical evidence from both scientific reductionists and emergentists, as well as their allies in philosophy, are presently all plausibly unsuccessful. However, I also detail how empirical evidence can be used to resolve the disputes in concrete scientific cases. My theoretical work thus illuminates how our Battle of the Ages is very much an ongoing one and rather different than even participants in the debates, let alone philosophers, have supposed. My work also supplies a platform from which to more productively engage the debates in the future.

Over coming posts, I outline the main lines of argument for these conclusions working through the book’s four parts. For a still more detailed overview of the book, here is a link to the Introduction at CUP’s website:



  1. Ken

    This is kind of tangential, but I was prodded to this by your allusion to what you might call “philosophical blinders” in not looking at scientific developments.

    Suppose one thought that there are just two options in the metaphysics of mind: Type identity theory and flat realization. Among the things you seem to be saying is that, no, there is another option. There might be compositional relations between mental entities and neuronal entities.

    • Ken

      I should probably have been more nuanced in my question. It’s not exactly that there are two options. Maybe it’s two “live” options. Something to set aside, say, dualism, behaviorism, etc.

      • Carl Gillett

        Hi Ken, thanks for the question. I think you are raising the question of what kind of “vertical” relation gets posited in what I am terming “compositional explanations”. I engage that in the next two posts I will put up, so why don’t I defer to those posts.

        Basically, I think we need to look again at compositional explanations and the “vertical” relations they posit. Once you do that, then you get a rather different view of the relations between levels in nature — whether cells and organs, proteins and cells, and “minds” and brains if they are different levels.

        The scientific reductionist and scientific emergentist positions I sketch in later posts also offer a couple of fresh options, building on top of the latter picture, for the relation of the psychological level and lower levels.

        So ask your question again after the next couple of posts.


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