Person

Sharon Street

American secular philosopher (b. 1972), Associate Professor of Philosophy at New York University. Author of the most influential contemporary evolutionary debunking argument against moral realism, the Darwinian Dilemma for Realist Theories of Value (Philosophical Studies 127, 2006).

Street's codex relevance is asymmetric: she is a secular philosopher whose argument is one of the most-cited atheist-internal critiques of atheistic moral realism, and therefore a key resource for the Christian apologetic case that materialism cannot ground objective moral values. The codex uses Street's argument in the Moral Arguments family, the Atheist Moral Realism Objection defeater, and the broader case that the moral landscape favors theism over secularism.

She is not a Christian or a theist; she is an anti-realist who concludes that we should abandon moral realism rather than seek a divine grounding for it. Her argument is therefore dialectically useful for Christian apologetics in a specific way: an atheist herself is showing that atheism + moral realism is unstable. The codex cites her with appropriate respect for the secular position while deploying the argument for theistic purposes.

Biographical sketch

• Education: B.A. Princeton (1995); Ph.D. Rutgers (2003, philosophy, supervisor Derek Parfit).
• Academic appointment: NYU Department of Philosophy since 2003.
• Personal positions: Self-identifies as a secular humanist; her metaethical position is a sophisticated form of moral anti-realism (specifically, a constructivist / Humean view inspired by Hume and Parfit).

The Darwinian Dilemma

Street's signature paper, "A Darwinian Dilemma for Realist Theories of Value" (Philosophical Studies 127, 2006), presents the following argument structure against moral realism:

1. Premise (empirical): Our moral beliefs and intuitions are substantially the product of evolutionary processes (natural selection pressures on social mammals leading to in-group cooperation, kin altruism, reciprocal altruism, etc.).
2. Premise (metaethical): Realist moral theories hold that there are moral facts that exist independently of our beliefs about them, robust, mind-independent normative truths.
3. The dilemma: Either (a) our evolved moral beliefs track the alleged independent moral facts, or (b) they do not.

• If (b), then moral realism collapses into moral skepticism, we have no reason to think our moral intuitions are reliable, because they were selected for survival, not for tracking moral truth.
• If (a), then we need an explanation of why selection for survival happens to align with tracking independent moral facts. Such an alignment would be an extraordinary coincidence requiring justification. No naturalistic story has been offered that makes the alignment non-coincidental.

4. Conclusion: Moral realism, on the empirical assumption of evolutionary origins, faces an unanswerable explanatory challenge. The rational response is to abandon moral realism, not to claim implausible alignment.

Street is herself an anti-realist: she concludes that we should abandon robust moral realism in favor of a constructivist / Humean position in which moral facts are mind-dependent (constructed by valuing agents) rather than mind-independent.

The codex's apologetic deployment

The Christian apologetic move (as developed in Atheist Moral Realism Objection and Moral Arguments):

1. Concede Street's empirical premise, yes, human moral intuitions have evolutionary origins.
2. Concede Street's argument against atheist moral realism, if evolution is the only source of our moral beliefs, the realist tracking-claim is implausible.
3. Reject Street's anti-realist conclusion, moral anti-realism is itself self-undermining (the anti-realist deploys moral language while denying the realism that gives it weight) and pastorally unlivable (the Holocaust was evil, not just disapproved-by-our-evolved-instincts).
4. Propose the theistic alternative, on theism, moral facts are grounded in God's nature, and human moral intuitions track them because God created humans with conscience-faculties calibrated to recognize moral truth (per Romans 2:14-15; see Argument from Conscience). The theist explains the alignment Street's argument exposes as unexplainable on naturalism.

The apologetic punch: Street's argument is a problem for atheist moral realism, and atheist moral realism is the position most secular moral realists hold. The Christian framework solves the dilemma she exposes; the secular framework cannot. Erik Wielenberg and other contemporary atheist moral realists have attempted responses, but none has satisfied Street, atheist-internal critics, or the broader debate. See Atheist Moral Realism Objection for the full deployment.

Other work

Street has also written substantially on:

• Constructivism in ethics, defending the constructivist alternative to realism ("What Is Constructivism in Ethics and Metaethics?", Philosophy Compass 5/5, 2010).
• Practical reasoning under uncertainty, work on how to make decisions when ethical theory itself is uncertain.
• The relationship between metaethics and normative ethics, extensive engagement with Parfit's On What Matters (2011).

She is part of the broader "Humean / constructivist" anti-realist tradition in contemporary metaethics, alongside Christine Korsgaard, Allan Gibbard, and (in different shapes) Simon Blackburn.

See also

• Atheist Moral Realism Objection, the codex's defeater hub against secular moral realism; Street's Darwinian Dilemma is the killshot move
• Moral Arguments, the broader Christian apologetic family Street's argument indirectly supports
• Argument from Conscience, the conscience-as-witness Christian response to evolutionary debunking
• Atheism (concept hub), references Street in the moral-naturalism critique
• Morality (concept hub), references Street in the metaethical positions table
• Erik Wielenberg, the contemporary atheist-realist position Street's argument targets
• J.L. Mackie, the atheist-philosopher predecessor (error theory rather than constructivism)
• Cumulative Case for Christian Theism, the meta-argument context
• Conscience (if exists) / Innate Knowledge of God, the theistic-grounding alternatives Street rejects