Peter Singer's 1975 argument for animal liberation was once dismissed as philosophical eccentricity. Today, factory farming faces sustained ethical scrutiny across democracies, corporate ESG frameworks, and even culinary institutions. This trajectory—from marginal claim to institutional norm—instantiates a pattern that experimental philosophers Buchanan and Powell have systematically documented: certain moral changes appear directional, cumulative, and resistant to reversal.

Yet moral progress remains philosophically contested. Metaethical relativists argue that cross-cultural moral disagreement precludes any progress claim, while error theorists deny the moral facts required to ground such claims. Recent findings in moral psychology—particularly work by Greene, Bloom, and Haidt—complicate both positions by revealing the cognitive architecture underlying our moral judgments and its evolutionary constraints.

The empirical turn in ethics offers a way through this impasse. Rather than presupposing moral realism or relativism, we can identify structural features of moral change that plausibly track improvement: expanded consistency, better integration with non-moral facts, and reduction of demonstrable suffering. This article synthesizes converging evidence from evolutionary psychology, historical moral epidemiology, and cognitive science to defend a modest but genuine notion of moral progress—one that acknowledges disagreement without conceding to skepticism.

The relativist challenge presumes that without a fixed moral endpoint, all moral change is merely lateral variation. But this conflates directionless with directionally underdetermined. Buchanan and Powell's work on the evolution of moral progress identifies specific criteria—inclusivity, consistency, and factual accuracy—that operate as internal standards of moral reasoning itself.

Consider factual accuracy first. Moral judgments about witches, homosexuality, or racial hierarchy depended on empirical claims about metaphysics, psychology, and biology that we now know to be false. Nichols and Knobe's experimental work demonstrates that when subjects learn the empirical presuppositions of their moral judgments are mistaken, their judgments systematically revise. This is not arbitrary change; it is error correction.

Consistency provides a second indicator. Peter Singer's expanding circle argument, refined by subsequent experimental philosophers, shows that many moral positions rely on morally arbitrary distinctions—species membership, geographic proximity, temporal distance. When these distinctions are made salient through reflection, judgments tend to move toward greater consistency. This dynamic mimics Rawlsian reflective equilibrium under empirical constraint.

The third criterion, inclusivity, reflects what Greene calls the metamorality problem: how tribally-evolved moral cognition adapts to increasingly interconnected societies. Progress here means the extension of moral concern to previously excluded parties whose exclusion cannot survive scrutiny under the first two criteria.

Together, these indicators provide a non-question-begging framework for identifying progress. They don't require metaphysical moral realism, only that moral reasoning has internal standards. A shift satisfies progress conditions when it demonstrably better meets these standards than what it replaced.

Takeaway

Moral progress doesn't require a fixed endpoint—only that our moral judgments become more consistent, more empirically accurate, and less dependent on arbitrary exclusions than what came before.

The historical trajectory across multiple moral domains exhibits a striking pattern. Pinker's compilation of violence statistics in The Better Angels of Our Nature, though contested in specifics, documents order-of-magnitude declines in interpersonal violence, judicial cruelty, and warfare deaths per capita. More importantly for our purposes, these declines correlate with shifts in the scope of moral consideration.

The abolition of chattel slavery provides the paradigm case. Kwame Anthony Appiah's honor-based analysis, supplemented by Christopher Brown's historical work, demonstrates that abolition succeeded not through novel moral arguments—the wrongness of slavery had been articulated for millennia—but through the collapse of empirical rationalizations sustaining moral exclusion. This pattern recurs: women's suffrage, decolonization, and gay rights each involved dismantling factual pretenses for exclusion.

Contemporary experimental work by Waytz, Iyer, and colleagues on moral circle measurement reveals that individual variance in inclusivity predicts specific policy attitudes and cross-cultural cooperation. Longitudinal data suggests population-level expansion, though not monotonically—Nazi Germany and the Rwandan genocide represent devastating regressions. Progress is not inevitable, but it is possible and, in aggregate, historically observable.

The animal case deserves particular attention. As Singer predicted, expanding moral consideration to non-human animals has followed the same trajectory: initial dismissal, empirical challenges to human uniqueness claims (cognitive ethology, pain research), gradual institutional accommodation. De Waal's primatological findings systematically eroded the cognitive-moral distinction between humans and other animals.

Critically, these expansions rarely contract upon reflection. Once moral concern extends to a group, subsequent generations don't typically re-question the extension. This ratchet-like property distinguishes genuine progress from fashion or ideology.

Takeaway

The ratchet effect matters: moral expansions rarely reverse under scrutiny, suggesting they encode genuine cognitive achievements rather than arbitrary cultural drift.

Understanding how moral progress occurs requires attention to the dual-process architecture of moral cognition. Greene's neuroimaging research reveals two distinct systems: rapid, emotionally-driven intuitions rooted in evolutionary heuristics, and slower, controlled deliberation capable of overriding those intuitions. Progress typically involves the latter recruiting against the former, extending impartiality beyond tribal defaults.

But cognition alone doesn't explain progress. Cecilia Heyes' work on cognitive gadgets highlights that many moral capacities are culturally transmitted rather than innate. Literacy, in particular, appears to be a moral technology—it enables perspective-taking with distant others through narrative, a mechanism Steven Pinker credits with humanitarian revolutions.

Institutional design amplifies these cognitive shifts. Rule-of-law systems, market interdependence, and democratic deliberation create conditions where tribal moral intuitions face systematic challenge. Robert Wright's non-zero-sum analysis shows how expanding cooperative networks make broader moral consideration strategically as well as normatively advantageous—a rare alignment.

The role of moral entrepreneurs deserves emphasis. Empirical historical work suggests progress often depends on committed minorities who articulate previously unarticulated inconsistencies. Cass Sunstein's work on norm cascades demonstrates how such articulations can rapidly restructure moral common ground when latent inconsistencies reach a tipping point.

Finally, technological change reshapes the moral landscape. Contraception transformed sexual ethics; imaging revealed fetal development; the internet made distant suffering visible. Each innovation exposed the empirical contingency of previously naturalized moral positions. Progress, in this view, is neither guaranteed nor illusory—it is the likely outcome when reflective cognition, cultural transmission, and technological transparency operate under conditions favorable to inconsistency detection.

Takeaway

Moral progress emerges from a specific ecology: reflective cognition meeting cultural transmission meeting technological transparency. Understanding this ecology helps us cultivate it deliberately.

The empirical case for moral progress is neither triumphalist nor complacent. It requires no commitment to moral realism, no guarantee of continued improvement, and no denial that regressions occur. It requires only that moral reasoning has internal standards—consistency, empirical accuracy, inclusivity—by which some moral positions can be judged better-supported than others.

This modest realism has practical stakes. If moral progress is possible, then which conditions enable it becomes urgent: institutional design, literacy, deliberative infrastructure, technological transparency. The alternative—treating moral change as arbitrary drift—forecloses the very reflection that has historically driven improvement.

For AI ethics specifically, the framework has direct implications. Aligning artificial agents with human values requires distinguishing values worth preserving from those that better reflection would revise. Recognizing progress conditions offers guidance where mere value aggregation would encode current prejudices as permanent constraints.