Experiment #116 · Thought experiment

Singer's Expanding Circle

Moral consideration extends outward over history

Peter Singer (building on W. E. H. Lecky) · 1981 · Ethics

First published: P. Singer, *The Expanding Circle: Ethics and Sociobiology* (1981).

Moral concern has expanded historically — from family, to tribe, to nation, to humanity, to sentient animals. The trajectory is the test of moral progress.

Singer argues that moral progress consists in the progressive extension of the circle of beings whose interests command consideration: from immediate kin, to tribe, to nation, to all humans, to sentient animals, and (in some readings) eventually to all morally considerable entities. The expansion is, on Singer's reading, not arbitrary but tracks the recognition of morally relevant similarities. The framework licenses animal-rights ethics and provides Singer's primary argument structure: every expansion of the circle has been resisted in its time but later seems obvious. The case is a foundational reference for utilitarian, sentience-based, and effective-altruist ethics.

Formulation

Moral circle = set of beings whose interests command consideration. Historical trajectory: kin → tribe → nation → humanity → sentient animals → … Moral progress = principled expansion of the circle on grounds of relevant similarity (sentience, interests).

Compare this experiment

Dimensions Engaged

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Observer

Engages Observer · Agency in collective-historical mode: moral consideration extends from immediate to remote bearers of interests.

Responses — How Schools Engage

Affirms / takes the bait 3

Naturalism

Compatible with utilitarian and consequentialist naturalism: sentience is the morally relevant feature, and circle-expansion tracks the principled recognition of it.

Liberation Theology

Compatible with the expansion of moral concern to oppressed groups; though liberation theology grounds the expansion theologically rather than in sentience alone.

Deep Ecology

A natural extension: the circle expands not just to sentient animals but to ecosystems and species, with intrinsic moral weight.

Denies / rejects the premise 1

Confucianism

Confucian ethics insists on graded obligations: family before strangers, near before far. The expanding-circle narrative violates the natural structure of moral obligations.

Reframes the question 2

Pragmatism

Moral progress is messier than a single-circle expansion narrative; what looks like progress in one dimension may be regress in another. The metaphor is suggestive but not normative.

Existentialism

Moral life cannot be reduced to a metric of which beings are inside the circle; the deeper question is how authentic moral engagement is sustained at any scale.