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Marc’s research areas are philosophy of biology, philosophy of science, and metaphysics.  He has conducted research on a variety of topics, including biological species, natural kinds, scientific classification, individuality, historicity, and homology.  See below for selected publications and unpublished work.

Natural Kinds, Classification, and Scientific Practice

Scientists have a variety of epistemic and pragmatic reasons for classifying.  Some scientists are interested in classifications of kinds that underwrite induction. Others are interested in causal kinds.  Some scientists construct classifications that capture historical sequences.  And other scientists aim to produce classifications of stable and reproducible kinds.  Philosophers tend to posit overarching, universal accounts of natural kinds that focus on an aspect of scientific classification (for example, holding that all natural kind classifications should underwrite induction).  As a result, most philosophical accounts of kinds fail to capture the variety of epistemic and pragmatic aims scientists have for classifying.

The project “Natural Kinds, Classification, and Scientific Practice” aims to refocus philosophical work on natural kinds by carefully studying successful classificatory practices in science.  That requires developing an account of kinds that is sensitive to the diverse epistemic and pragmatic reasons scientists have for positing classifications.  This project has two underlying motivations.  One is the need for an account of kinds that helps us understand why our best classificatory practices help us control and manipulate the world.  That is, an account that helps us understand why natural kind classifications in science are epistemologically fruitful.  Another motivation is to offer an account of kinds that is both sensitive to the diverse reasons scientists have for positing classifications and also gives guidance in determining whether a posited category is a natural kind.  We need, in other words, an account of kinds that helps us to determine where to place our ontological commitments.

Another aspect of the project is to replace the mind independence requirement that philosophers typically place on natural kinds.  Many philosophers require that natural kinds exist independently of human thought.  For example, the element gold exists independent of human thought, whereas post dramatic stress syndrome does not.  However, the mind independence requirement on natural kinds is problematic.  Many classifications of kinds that help us achieve our epistemic and pragmatic aims refer to kinds of entities, psychological states, and behaviors that depend on us.  One idea Marc is exploring is to replace the mind independence requirement with the notion of external defeasibility from epistemology.  Natural kind classifications should be defeasible.  This requirement allows that successful classifications from biology, psychology, and sociology are natural kinds, yet it rules out categories that are true by convention.

Biological Individuality

Standard philosophical and biological accounts of individuality take us (humans, mammals, eukaryotes) to be paradigmatic individuals or organisms.  However, most of life is not like us, but is single cellular (e.g., microbes and protists).  Because most of life is not like us, standard accounts of biological individuality leave out much of the organic world.

To rectify this problem Makmiller Pedroso and Marc have explored the individuality of microbes and especially microbial communities.  They have focused on biofilms.  Biofilms are ubiquitous –they live on our teeth (dental plague), they live in our hearts, in our guts, in ponds, on damp heater vents, and cooling towers.  Many biofilms have properties that make them good candidates for individuals, particularly individuals in selection. The cells in a biofilm share genes, communicate, coordinate their activities, give rise to biofilm adaptations, and transmit those adaptations across generations of biofilms.  In a series of articles Marc and Mak argue that the case of biofilms demonstrates that we need a more pluralistic account of individuality, an account that better captures the diversity of biological individuals in the world.  We need an account of individuality that does not take us to be the paradigmatic individuals of the organic world.

Species and Biological Classification

Marc has worked on ‘the species problem’ (the problem of providing the right account of biological species) since the late 1980s.  He has written numerous publications on species, including two books, The Poverty of the Linnaean Hierarchy and The Units of Evolution.  His contributions on species and biological taxonomy include developing a variant of species pluralism and calling into question the fruitfulness of the Linnaean Hierarchy.  He has also written on Darwin’s view of species.  He has contributed to the debate over the ontological status of species, and more recently has argued that new essentialist approaches to species (including Homeostatic Property Cluster Theory) don’t accurately capture biological taxonomy.

Biological Homology

A biological homologue is a trait found in two organisms, and that trait is the result of those organisms having a common ancestry.  For example, wings are homologous among birds.  But wings are not homologous between birds and insects –wings arose independently in birds and insects.  Biological homology is a rich philosophical topic, because instances of homologues can be of the same type even though they are quite dissimilar.  The study of homology brings up classic metaphysical questions concerning identity and difference.

In a series of articles Marc explores the nature of homology.  In one article he suggests that studying biological work on behavioral homologies can shed light on psychological categories.  In another article, he posits that ‘Homology Thinking’ is a major way that biologists understand similarity and difference among organisms.  Gunter Wagner (2016), a leading biologist on homology and development, believes that homology thinking, along side population thinking and tree thinking, is a major conceptual tool that biologists use to understand life’s diversity. 


What makes an entity a historical entity?  What makes an explanation a historical explanation?  These are vexing questions. Marc has applied the idea of path dependency to help us understand the historical nature of species and homologies.  Then there are more general questions about historicity:  What is historical about historical explanations, and how are historical explanations different from other types of explanations?  Marc thinks that historical explanations are different from other types of explanations.  He has some ideas about that difference that need further development.

Health and Disease, and Human Nature

Several years ago Marc was unhappy with how philosophers employ the notions of ‘natural’ and ‘normal’ when defining ‘health’ and ‘diseases’ and when arguing for positions in environmental ethics.  He thinks there is a common error in these two areas of research.  Philosophers and others assume that we can draw on biological theory to determine what is natural or normal and then use that information to solve philosophical problems.  Following Elliott Sober (1980), Marc believes that biology does not tell us on what is natural or normal.  He has written several papers on the topic: “Defining ‘Health’ and Disease,” “Where the Wild Things Are: Environmental Preservation and Human Nature,” and “Bridging the Gap Between Human Kinds and Biological Kinds.”

Marc’s research has been funded by various agencies, including the Social Sciences and Humanities Research Council of Canada, the National Science Foundation (USA), the Canadian Institutes of Health Research, the Killam Trust, the Leverhulme Trust, the Templeton Foundation, and the Mellon Foundation.  The University of Calgary has also been very supportive of Marc’s research.

Selected Publications

2002.  Psychological Categories as Homologies: Lessons from Ethology.  Biology and Philosophy, 22: 659-74.

2009.  Health and Disease.  Studies of History and Philosophy of Biological and Biomedical Sciences, 40 (3):221-7.

2010.  Darwin's Solution to the Species Problem. Synthese, 175: 405-25.

2010.  Microbiology and the Species Problem.  Biology and Philosophy, 25: 553-68.  

2010.  What's Wrong With the New Biological Essentialism?  Philosophy of Science, 77: 674-85.

2011.  Mystery of Mysteries: Darwin and the Species Problem. Cladistics, 27: 67-79.

2012.  Concepts of Protistology: Species Definitions and Boundaries (with Jens Boenigk, Kerstin Hoef-Emden, James Mallet, and David Bass). European Journal of Protistology, 48:96-102.

2012.  Homology Thinking.  Biology and Philosophy, 27: 381-400

2013.  Biological Individuality: the case of biofilms (with Makmiller Pedroso). In Biology and Philosoph,  28: 331-49.

2014.  Consilience, Historicity, and the Species Problem.  In Evolutionary Biology: Conceptual, Ethical, and Religious Issues, Thompson and Walsh (eds.).  Cambridge University Press.

2014.  Species Historicity and Path Dependency.  Philosophy of Science, 81: 714-26.

2015.  Rethinking Evolutionary Individuality (with Makmiller Pedroso).  Proceedings of the National Academy of Sciences,
112: 10126-32.

2015.  Scientific Kinds (with Thomas A.C. Reydon).  Philosophical Studies, 172 (4):969-86.

2016.  What Biofilms Can Teach Us About Individuality (with Makmiller Pedroso).  Individuality Across the Sciences Guay and Pradeu (eds.), 103-121)Oxford University Press.

Unpublished Work

Science and Metaphysics: Lessons from Microbiology

SSHRC Grant: Natural Kinds, Classification, and Scientific Practice

Natural Kinds, Classification and Scientific Practice