20th Century Emergentism A Framework for Emergence Examples Formulating Emergence in the Physical Sciences Sebastian De Haro University of Amsterdam and University of Cambridge Emergence, Effectiveness, & Equivalence in Physics 19 October 2018 Sebastian De Haro Formulating Emergence in the Physical Sciences 20th Century Emergentism A Framework for Emergence Examples Aim of the talk The aim of this talk is to introduce and illustrate a criterion for emergence. The framework is formal, where by `formalization' I mean a conceptual schema detailed enough that it admits the basic notions of sets and maps. Formalization is here not a goal, but a tool. The goal is to be able to more easily analyse examples in physics. The framework will empahsise emergence as being an interpretative, rather than a merely formal, relation between theories. Sebastian De Haro Formulating Emergence in the Physical Sciences 20th Century Emergentism A Framework for Emergence Examples Aims of this project I discuss ontological emergence: but the immediate aim of the project is not strongly metaphysical, in the sense of requiring a commitment to a specific metaphysics, and explicating emergence in those terms. My aim is to clarify what we mean by `ontological emergence' in general: and to give a criterion that is as straightforward as possible. I aim to give a minimal account of ontological emergence, independently of whether we are e.g. Humeans or Aristotelians about causation| further metaphysical details then just adding to the basic picture that I will present. One danger I wish to avoid is to make the conception of ontological emergence depend on specific metaphysical notions. `Ontology' will be here understood in the straightforward sense of `the ontology of a scientific theory', i.e. the domain of application that a theory describes, under a given interpretation. This domain of application is a part of the empirical world, not a matter of language in Quinean fashion. Sebastian De Haro Formulating Emergence in the Physical Sciences 20th Century Emergentism A Framework for Emergence Examples Outline 1 20th Century Emergentism The British Emergentists The New Emergentists 2 A Framework for Emergence Scientific theories Being more precise about emergence Ontological emergence 3 Examples Masslessness Ontology Sebastian De Haro Formulating Emergence in the Physical Sciences 20th Century Emergentism The British Emergentists A Framework for Emergence The New Emergentists Examples 20th Century Emergentism One well-known definition of emergence, by C. D. Broad: `Put in abstract terms the emergent theory asserts that there are certain wholes, composed (say) of constituents, A, B and C in a relation R to each other; that all wholes composed of constituents of the same kind as A, B and C in relations of the same kind as R have certain characteristic properties; that A, B and C are capable of occurring in other kinds of complex where the relation is not of the same kind as R; and that the characteristic properties of the whole R(A; B; C) cannot, even in theory, be deduced from the most complete knowledge of the properties of A, B and C in isolation or in other wholes which are not of the form R(A; B; C).' (Broad, 1925, 61) Drawback: does this definition actually apply to anything in physics? Recent accounts of emergence have attempted to give positive construals of the notion: Humphreys (1997, 2016), Batterman (2002), Butterfield (2011), Guay and Sartenaer (2016), Crowther (2016). Sebastian De Haro Formulating Emergence in the Physical Sciences 20th Century Emergentism The British Emergentists A Framework for Emergence The New Emergentists Examples The New Emergentists: Anderson vs. Weinberg The recent new wave of emergentism in physics can be traced back to `More is Different’ (1972) by Nobel Prize winner Philip Anderson: The laws and principles he studies as a condensed matter physicist are emergent, in the sense that they are entirely different from, but have no lower status than, those studied by particle physicists. Anderson accepts reduction but not constructionism: `The reductionist hypothesis does not by any means imply a \constructionist" one: The ability to reduce everything to simple fundamental laws does not imply the ability to start from those laws and reconstruct the universe. The more the elementary particle physicists tell us about the nature of the fundamental laws, the less relevance they seem to have to the very real problems of the rest of science.' Famously opposed by Nobel Prize winner Steven Weinberg: the physics of the very small hold a privileged position in a hierarchy of scientific explanation. (Cf. Mainwood (2006)). Sebastian De Haro Formulating Emergence in the Physical Sciences 20th Century Emergentism The British Emergentists A Framework for Emergence The New Emergentists Examples Ramifications with science funding The debate was taken to the US House of Representatives over the funding of the Superconducting Super Collider (SSC): Anderson: `I emphasized the almost complete irrelevance of the results of particle physics not only to real life but to the rest of science, while arguing that they are in no sense more fundamental than what Alan Turing did in founding the computer science, or what Francis Crick and James Watson did in discovering the secret of life.' Weinberg: `One of the members of the [SSC] board argued that we should not give the impression that we think that elementary particle physics is more fundamental than other fields, because it just tended to enrage our friends in other areas of physics. The reason we give the impression that we think that elementary particle physics is more fundamental than other branches of physics is because it is. I do not know how to defend the amounts being spent on particle physics without being frank about this.' Sebastian De Haro Formulating Emergence in the Physical Sciences 20th Century Emergentism The British Emergentists A Framework for Emergence The New Emergentists Examples The project was discontinued in 1993... Sebastian De Haro Formulating Emergence in the Physical Sciences 20th Century Emergentism Scientific theories A Framework for Emergence Being more precise about emergence Examples Ontological emergence An informal description of emergence Emergence is an ubiquitous phenomenon in nature. It is, roughly, the observation that there are \higher-level" phenomena (or entities, or theories), that appear in the macroscopic world, and which are absent from the \lower-level", or microscopic, world. More precisely, I will agree with the literature in seeing emergence as a \delicate balance" between: (A) Dependence, linkage or rootedness. (B) Independence, autonomy or novelty. See e.g. Humphreys (2016: p. 26), Bedau (1997: p. 375), Bedau and Humphreys (2008: p. 1), Butterfield (2011: x1.1.1), Crowther (2016: p. 42). I will discuss emergence in terms of theories (i.e. I will say that `theory X is emergent with respect to theory Y '), but this can equally well be put in terms of `entities', `properties' or `behaviour'. Sebastian De Haro Formulating Emergence in the Physical Sciences 20th Century Emergentism Scientific theories A Framework for Emergence Being more precise about emergence Examples Ontological emergence Coordinates for this talk The example I shall give will not be a case of mereology (i.e. \parts and wholes"/microscopic vs. macroscopic physics): while important, I believe it easily can lead to confusion, and we ought to look at easier examples first! Mereology is not essential for emergence (Batterman (2002)). The kind of emergence I will concentrate on here could be called conceptual: emergence of theories, entities, properties or behaviour as we link different situations or systems through a relation of resemblance (linkage). (I expect that the framework can be applied to mereology as well. But this will not be my focus.) Discussions of emergence in e.g. the philosophy of mind emphasise causation and-or powers. The new wave of emergence in physics has not focused on these notions, but rather on entities. Perhaps because causation comes in less naturally in modern physics than in Newtonian (`ball-bearing') physics. Sebastian De Haro Formulating Emergence in the Physical Sciences 20th Century Emergentism Scientific theories A Framework for Emergence Being more precise about emergence Examples Ontological emergence An Example: Ferromagnetism Consider an iron bar in a strong external magnetic field, H, parallel to its axis. The bar will be almost completely magnetized. Now decrease H to zero, for T < TC: M will decrease, but not to zero. Rather, at zero field it will have a spontaneous magnetization, M0. Reversing the field will reverse the magnetization, so M must be an odd function. Thus its graph is of the type (Baxter 1982): Figure: Graph of M(H) for T < TC. Sebastian De Haro Formulating Emergence in the Physical Sciences 20th Century Emergentism Scientific theories A Framework for Emergence Being more precise about emergence Examples Ontological emergence An Example: Ferromagnetism For T > TC, there is no net magnetization when we remove the external magnetic field, and so the graph looks like: Figure: Graphs of M(H) for: (b) T > TC and (c) T = TC. Sebastian De Haro Formulating Emergence in the Physical Sciences 20th Century Emergentism Scientific theories A Framework for Emergence Being more precise about emergence Examples Ontological emergence An Example: Ferromagnetism The spontaneous magnetization is a function of the temperature, and can be defined as: M0(T ) = lim M(H; T ) : H!0+ It is positive for T < TC and zero for T > TC: Figure: The spontaneous magnetization M0 as a function of temperature. Sebastian De Haro Formulating Emergence in the Physical Sciences 20th Century Emergentism Scientific theories A Framework for Emergence Being more precise about emergence Examples Ontological emergence An Example: Ferromagnetism The behaviour near the critical (Curie) temperature is appropriately described by the critical exponent, β: β − M0(T ) ∼ (−t) ; as t ! 0 ; t := (T − TC)=TC : Critical exponents can be calculated in a variety of ways (using the Ising model for the ferromagnet, renormalization group techniques, etc.).