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Durham University

Durham Emergence Project


The case of Piezoelectricity


Alexandru Manafu (Principal Investigator)

Riccardo Spezia

Maximilian Kistler

David Zarebski

Project Description

In recent years, many philosophical discussions about emergence have shifted focus from the philosophy of mind to the philosophy of the physical sciences. It has been suggested that physics presents us with emergent phenomena or that chemistry is the embodiment of emergence. Many of the discussed examples of emergent phenomena come from the study of materials, such as phase transitions, superconductivity, ferromagnetism and antiferromagnetismes, and the quantum Hall states.

Our project explored the existence of emergent phenomena in materials. The fact that the physical and chemical properties of materials can be intersubjectively scrutinized, that they are amenable to measurement, to experiment and to a quantitative understanding to a greater extent than those in other special sciences, makes the study of materials an ideal domain for the investigation of emergence.

A material is said to be piezoelectric if the application of an external mechanical stress gives rise to electric polarization (direct effect) and it experiences mechanical deformations when placed in an electric field (converse effect). The piezoelectric effect is defined by the following equations:



where P is polarization, T is stress, S is strain, E is the intensity of the electric field, and d is the piezoelectric coefficient of the material.

Piezoelectricity is as philosophically interesting as it is technologically useful. The definition of piezoelectricity is functional (describes a behaviour under certain conditions) and phenomenological in the sense that it is agnostic about the mechanism. Many types of materials are considered piezoelectric: crystals (quartz, Rochelle salt), manmade materials (ceramics like lead zirconate titanate, PZT, polymers like polyvinylidene fluoride, PVDF), cement, gels (agar), materials of biological origin (bone, collagen). From a philosophical standpoint, it is tempting to view piezoelectricity as a case of multiple realization. Also, piezoelectricity has been described as “one of the most useful of broken symmetry phenomena as it manifests itself in condensed matter systems” (Anderson 2004). Since multiple realizability and broken symmetry are two ways in which philosophers and physicists have thought about emergence, our project investigated whether piezoelectricity is an emergent phenomenon.

We argued that piezoelectricity should be understood as a functional property, i.e., a property that many materials can exhibit, which is carried out by different mechanisms in different materials. Therefore, in a certain sense, piezoelectricity is an emergent property of materials.

Click here for more information and the project's website.


Emergence in Materials, Interdisciplinary Workshop, May 25-27 2015, held at IHPST in Paris

May 25th:
10:00-11:00 Thomas Vogt: Towards a philosophy of materials science
11:15-12:15 Margaret Morrison: Turbulent Flows, Universality and Emergence
2:00-3:00 Jean-Pierre Llored: Chemical Materials and Emergence
3:15-4:15 Karim Thebault: The Hawking Effect as an Emergent Phenomenon?

May 26th:
10:00-11:00 Alexandre Guay & Olivier Sartenaer: Emergent quasiparticles: the case of the fractional quantum Hall effect
11:15-12:15 Alex Manafu: Piezoelectricity as an Emergent Property?
2:00-3:00 Michael Berry: The singularities of light: intensity, phase, polarization
3:15-4:15 Sorin Bangu: When causation is not the point: Individualism v. Collectivism on Explanation

May 27th:
10:00-11:00 Shaul Katzir: Macro and microphysical explanations of piezoelectricity before WWII
11:15-12:15 Robert Batterman: Asymptotics, Minimal Models, Multiscale Techniques
2:00-3:00 Olimpia Lombardi: From reduction to emergence: distinguishing between intratheory and intertheory emergence
3:15-4:15 Joachim Schummer: Material Emergence in Chemistry: The Standard Case


Edited volume

Emergent Phenomena in Materials. Special issue. It will contain most of the contributions of the speakers in the interdisciplinary conference Emergence in Materials which we organized at IHPST in Paris in May 2015). We are now in discussions with Foundations of Physics for publishing the papers as a special issue of that journal.

Articles/ Book Chapters

• Manafu, A. (2015) “The Prospects for Fusion Emergence” In Sandu, G., Parvu, I., and Toader, I., editors, Romanian Studies in Philosophy of Science, Boston Studies in the Philosophy and History of Science. Volume 313, pp. 221-235.

• Manafu, A. (2015) “A Novel Approach to Emergence in Chemistry” In Scerri, E., and McIntyre, L., editors, Philosophy of Chemistry. Growth of a New Discipline. Boston Studies in the Philosophy and History of Science. Volume 306, 2015, pp. 39-55.

• Manafu, A. (draft) For a Functional Understanding of Piezoelectricity

• Manafu, A. (under review at BJPS) Microstructuralism. An analysis.

• Matias Velasquez & Alex Manafu (draft in progress) Emergence at the Core of Crystal Chemistry

Bibliography on Emergence

David Zarebski created the ultimate bibliography on Emergence – a resource that contains virtually every single philosophical and scientific paper about emergence ever published. David used text analysis and data mining software on a large number of philosophical and scientific texts (thousands of journal articles and hundreds of books). It has thousands of entries from many fields and it is available at: