Cambridge University Press · 2007

The Structural Evolution of Morality

by J. McKenzie Alexander

London School of Economics

It is certainly the case that morality governs the interactions that take place between individuals. But what if morality exists because of these interactions? This book argues that much of the behaviour we view as 'moral' exists because acting in that way benefits each of us to the greatest extent possible, given the socially structured nature of society.

Drawing on evolutionary game theory, the theory of bounded rationality, and computational models of social networks, it shows both how moral behaviour can emerge in socially structured environments, and how it can persist even when it is not typically viewed as 'rational' from a traditional economic perspective. The book also offers a theory of how moral principles and moral sentiments play an indispensable role in effective choice, acting as 'fast and frugal heuristics' in social decision contexts.

01About this book

Where earlier evolutionary accounts of morality typically assumed the random-encounter idealisation of standard game theory — every agent equally likely to interact with every other — this book takes seriously the fact that real social life is structured. We interact more often with our neighbours, our friends, our colleagues. The topology of the social network through which interactions flow makes a profound difference to which moral norms can emerge, persist, or be displaced.

Methodologically, the book uses evolutionary game theory and agent-based simulation as instruments of moral inquiry — not to reduce ethics to biology, but to ask which kinds of moral arrangements are stable against the perturbations of bounded rationality and shifting social structure. The four cardinal social phenomena examined — cooperation, trust, fairness, and retribution — emerge as different stable outcomes depending on the structure of interaction.

02Topics covered

Evolutionary game theory
Bounded rationality and learning
The emergence of cooperation
The evolution of trust
Fairness and bargaining
Retribution and punishment
Social network topology
Local interaction models
Fast-and-frugal moral heuristics
Moral sentiments and choice
Cultural evolution of norms
Naturalistic moral epistemology

03Reviews

This is an important book for philosophers as well as social scientists. It clearly models how pro-social behavior can emerge in social networks, and shows which network structures are most conducive to the development of co-operation, trust or fairness. The book advances our understanding of evolutionary games, since it makes them more realistic and applicable to the complex social structures we live in.

— Cristina Bicchieri, University of Pennsylvania
This work is certain to be invaluable to anyone following the road laid by Brian Skyrms. Additionally, I recommend this book to many of those unconvinced about the possibility of making the leap from an explanation of thin morality to a thick account.

— Jonathan Grose, Economics and Philosophy
Alexander's book remains an important contribution to enhance our understanding of morality through evolutionary lens. It calls for more theoretical and empirical research, while pointing to the necessity for granting more attention to the methodological issues discussed above.

— Cyril Hédoin, Œconomia

04About the author

J. McKenzie Alexander is Professor of Philosophy in the Department of Philosophy, Logic and Scientific Method at the London School of Economics. His research spans evolutionary game theory, decision theory, and the philosophy of social science, with a longstanding interest in the application of computational methods to philosophical problems.

His later books include Evolutionary Game Theory (Cambridge Elements, 2023) and The Open Society as an Enemy (LSE Press, 2024).