Introduction
Bonnie Steinbock’s “What’s Wrong with Adultery?” asks why extramarital sexual relationships are morally objectionable and whether moral disapproval justifies legal punishment. A careful answer must separate several questions that are often merged together: whether a person broke a promise, whether deception undermined a partner’s autonomy, whether emotional or financial harm occurred, whether sexual-health risks were imposed without informed consent, and whether the state should criminalize consensual adult behavior. Adultery is typically wrong in monogamous relationships because fidelity is part of an explicit or reasonably understood commitment. Secretly violating that commitment allows one partner to keep the benefits of the relationship while withholding information that might change the other partner’s choices about sex, finances, residence, parenting, or continuation of the marriage. The moral core is therefore not simply that sexual contact occurred outside marriage. It is the combination of breached agreement, deception, and foreseeable harm. This distinction also explains why consensual nonmonogamy presents a different ethical case when partners have openly agreed to different boundaries (Steinbock, 1986; Brake, 2012).
Promise, Trust, and Informed Choice
Marriage often involves shared expectations about sexual exclusivity, honesty, finances, caregiving, and long-term planning. When those expectations are mutually understood, fidelity becomes part of the basis on which each partner organizes important life decisions. Adultery undermines that structure because the unfaithful partner unilaterally changes the terms while allowing the other person to continue acting on false assumptions. This is morally significant even when the affair never becomes public and even when no pregnancy, infection, or financial loss occurs. Deception itself limits autonomy because the betrayed partner cannot make informed decisions about intimacy, health, money, or whether to remain in the relationship. The wrong therefore resembles other serious forms of promise-breaking in which one person benefits from another’s reliance while withholding material information. At the same time, promises should be interpreted according to the actual relationship rather than imposed by outsiders. If a couple has clearly agreed to consensual nonmonogamy, outside sexual activity does not automatically violate fidelity because the relevant commitment has been defined differently. Ethical judgment should focus on the agreement and the deception, not merely on marital status (Brake, 2012).
Emotional, Sexual, and Family Harms
Infidelity can create substantial emotional harm, including grief, anger, humiliation, anxiety, intrusive thoughts, distrust, and uncertainty about shared history. These outcomes are not identical in every relationship, but they help explain why adultery is rarely a purely private act affecting only the person who commits it. Sexual-health risks can also become morally important when one partner has unprotected contact outside the relationship and then exposes the spouse to infection without disclosure or informed choice. Similar concerns apply to pregnancy, shared finances, or the use of family resources to sustain an affair. Children may experience instability when adultery contributes to severe conflict, separation, divided loyalties, or disruption of caregiving, although it would be inaccurate to claim that every separation is worse for children than remaining in a chronically hostile household. Family consequences depend heavily on how adults respond after discovery. The strongest ethical argument therefore avoids exaggeration: adultery does not necessarily cause every possible harm, but secrecy can foreseeably create relational, health, financial, and parenting consequences that increase the seriousness of the betrayal (Fife et al., 2008).
Gender, Culture, and Double Standards
Adultery has historically been judged through unequal gender standards. In many legal and cultural systems, women’s sexual behavior was punished more severely because marriage was connected to inheritance, paternity, property, and male control of female sexuality, while men’s extramarital conduct was often tolerated unless it threatened another household. A defensible contemporary moral standard should reject that asymmetry. If adultery is wrong because it involves deception, breach of commitment, and nonconsensual risk, the same principle applies regardless of gender or sexual orientation. Ethical equality also requires attention to power. A financially dependent spouse, an employee involved with a supervisor, or a person facing social or immigration vulnerability may experience betrayal or coercion differently from someone with greater independence. Religious traditions may add covenantal or spiritual reasons for fidelity, while secular ethics may focus on trust, fairness, and autonomy. These approaches can coexist without assuming that one tradition supplies the only possible moral vocabulary. What matters is that judgment not rely on ownership, sexual double standards, or punishment aimed disproportionately at one group (Scales et al., 2010).
Moral Wrongdoing and Criminal Law
A serious moral wrong does not automatically require criminal punishment. Criminal law uses investigation, public prosecution, coercive sanctions, and sometimes imprisonment, so it requires stronger justification than private moral criticism. Adultery statutes also create difficult questions of definition and enforcement. A law must decide whether intercourse is required, whether emotional or digital affairs count, whether a consensually open marriage creates a defense, and how prosecutors will prove the couple’s private agreements. Selective enforcement is another danger because intimate conduct is usually hidden, allowing prosecution to fall disproportionately on people whose relationships become publicly exposed or politically useful. These problems support Steinbock’s distinction between condemning betrayal and criminalizing it (Steinbock, 1986). The state can address independently unlawful conduct—such as assault, coercion, fraud, exploitation, misuse of shared funds, or knowing transmission of serious infection—without making every act of consensual adultery a crime. Civil family law can also address property, support, and custody consequences where legally relevant. Proportionality therefore favors narrower legal responses to specific harms rather than general criminal regulation of infidelity.
Responsibility, Repair, and the Possibility of Reconciliation
Moral analysis should include what happens after betrayal because responsibility does not end when the affair is discovered. Repair may require ending deception, disclosing information relevant to sexual health and finances, accepting consequences, answering reasonable questions honestly, and allowing the betrayed partner genuine control over whether the relationship continues. Reconciliation cannot be demanded as proof of forgiveness, and separation does not necessarily mean that repair has failed. In some relationships, couples therapy can help rebuild trust when both partners participate voluntarily and no abuse makes joint counseling unsafe. Fife et al. (2008) emphasize that treatment after infidelity often requires attention to accountability, meaning, injury, and rebuilding trust rather than simply restoring the previous relationship as quickly as possible. The unfaithful partner should not focus solely on obtaining pardon because that repeats the earlier problem of controlling information and outcomes. Ethical repair is better understood as restoring agency to the person who was deceived. Whether the marriage continues or ends, responsibility involves truthfulness, respect for boundaries, and acceptance that consequences may be lasting.
Conclusion
Adultery is morally wrong in typical monogamous relationships because it violates an agreed or reasonably understood commitment, deceives a partner, restricts informed choice, and can produce emotional, sexual-health, financial, and family harm. The ethical problem is not captured adequately by defining adultery as any sexual contact outside marriage, because the meaning of fidelity depends on the partners’ actual agreement. Consensual nonmonogamy therefore differs from secret betrayal, while affairs involving coercion, fraud, professional exploitation, or deliberate exposure to harm contain additional wrongs that should be analyzed separately. Steinbock’s central insight is especially important: moral condemnation and criminal prohibition are not the same question (Steinbock, 1986). Criminal adultery laws are difficult to define consistently, invasive to enforce, and vulnerable to unequal application. A more proportionate response emphasizes honest agreements, accountability, counseling where appropriate, civil remedies for specific harms, and legal action when independent offenses occur. Fidelity remains morally significant because intimate relationships depend on trust, but the seriousness of betrayal does not require the state to police every consensual private relationship.
Works Cited
Brake, Elizabeth. Minimizing Marriage. Oxford University Press, 2012.
Fife, Stephen T., et al. “Treating Infidelity.” Journal of Marital and Family Therapy, vol. 34, no. 3, 2008.
Scales, Susan, et al. The Ethics of the Family. Cambridge Scholars Publishing, 2010.
Steinbock, Bonnie. “Adultery.” Philosophy & Public Policy Quarterly, vol. 6, no. 1, 1986, pp. 12–14.
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