Rational Constructivism in Ethics: Building Moral Judgments

What makes something morally right or wrong? Traditional answers point to divine command, fixed laws of nature, or timeless truths waiting to be discovered. But there is a strikingly different view: moral principles are not discovered – they are built. This is the core claim of rational constructivism in ethics, a position that places human reason and collective deliberation at the very center of moral life. Rather than looking to an independent moral reality “out there,” rational constructivism holds that ethical principles are the product of reasoned agreement among individuals. Understanding this view opens up some of the most important debates in moral philosophy – about autonomy, consensus, and what it truly means to act rightly.

What rational constructivism actually says 🔗

According to the Stanford Encyclopedia of Philosophy, constructivism in ethics is the view that normative truths – truths about what we ought to do – are determined by an idealized process of rational deliberation, choice, or agreement. This is a significant departure from moral realism, which holds that moral facts exist independently of any human mind or social process. It is also distinct from nihilism, which denies moral truth altogether. The constructivist occupies a middle ground: moral truths exist, but they depend on how rational agents would reason under the right conditions.

Put plainly, constructivism states that moral truths are neither invented nor discovered, but rather constructed by rational agents in order to solve practical problems. The principles that emerge from this process are not arbitrary – they carry genuine normative weight – but their authority is rooted in reason and agreement, not in some prior, stance-independent moral order.

The philosophical roots: Kant and the authority of reason 🔗

Rational constructivism draws its deepest inspiration from Immanuel Kant. The distinguishing feature of Kantian constructivism is that it understands the nature of moral and normative truths based on considerations about the basic features of rational agency. On this view, reasons for being moral do not spring from our personal interests or desires; they are rooted in our nature as rational beings. Because moral obligations are grounded in what reason itself requires, they apply universally and necessarily – to all rational beings, in all circumstances.

Kant’s critical insight was that ethics which depends on anything external to reason – a divine will, natural feeling, or social custom – fails to capture what makes morality genuinely authoritative. Such dependence, Kant called heteronomy: a form of moral unfreedom, where the agent is governed by forces outside their own rational will. Against this, constructivism insists that morality is a fundamentally cooperative enterprise, with the construction of reason’s authority providing a basis for offering others reasons for truth claims and moral claims.

Rawls and the original position 🔗

Contemporary discussion of constructivism in ethics largely originates in the work of John Rawls. Rawls wanted to develop principles of justice that could be accepted by all, without presupposing any particular religious doctrine or contested metaphysical view. His solution was an elegant thought experiment: the original position.

In the original position, a “veil of ignorance” prevents everyone from knowing their ethnicity, social status, gender, and their own ideas of how to lead a good life. Stripped of these details, individuals must choose principles of justice from behind this veil – principles they would accept regardless of where they end up in society. Because they cannot know whether they will be rich or poor, powerful or marginalized, rational self-interest leads them toward principles that are genuinely fair to everyone.

No party can press for agreement on principles that will arbitrarily favor the particular citizen they represent, because no party knows the specific attributes of the citizen they represent. The situation of the parties thus embodies reasonable conditions, within which the parties can make a rational agreement. The principles that emerge from this process are, for Rawls, constructed – not discovered – through a fair procedure of rational deliberation.

Rawls argued that rational deliberators behind the veil would converge on two core principles: equal basic liberties for all, and a rule that social and economic inequalities are only justified if they benefit the least advantaged members of society – his famous difference principle. By being ignorant of our circumstances, we can more objectively consider how societies should operate.

Three pillars of rational constructivism 🔗

Reason, not desire, as the foundation 🔗

Rational constructivism consistently holds that moral principles must be grounded in reason, not in preferences, emotions, or cultural habits. On this view, reasons for being moral do not spring from our interests or desires; instead, they are rooted in our nature as rational agents. Insofar as moral obligations are justified in terms of rational requirements, they are universally and necessarily binding for all rational beings. This is what separates constructivism from ethical relativism: the claim is not that “anything goes as long as people agree,” but that genuine moral principles must survive the scrutiny of rational deliberation.

Moral principles as constructed, not discovered 🔗

A central commitment of constructivism is its rejection of moral realism’s idea that there are ready-made moral facts we simply perceive or intuit. Kantian constructivism holds that moral objectivity is to be understood in terms of a suitably constructed social point of view that all can accept. Apart from the procedure of constructing the principles of justice, there are no moral facts. This is a bold claim – it means that the legitimacy of a moral principle depends not on its correspondence to some external standard, but on whether it could be endorsed by rational agents reasoning under appropriate conditions.

Consensus through rational deliberation 🔗

Rational constructivism treats ethical deliberation as a collaborative, ongoing process. Moral norms gain their authority from the agreement that could, in principle, be reached by rational individuals reasoning together under fair conditions. This does not mean moral principles are merely whatever any actual group happens to agree on – the agreement must be idealized, conducted by agents who are reasoning well, treating each other as equals, and setting aside arbitrary self-interest. Moral truths are constructed by a specified rational procedure. There is no prior, stance-independent moral order fully determining right and wrong; instead, the outcomes of the justificatory procedure constitute, or at least fix, moral truths.

Scanlon’s contractualism: what we owe each other 🔗

One of the most influential developments of the constructivist approach in recent philosophy is T.M. Scanlon’s contractualism, laid out in his landmark 1998 work What We Owe to Each Other. Contractualism is a constructivist attempt at providing a unified account of the subject matter of a central part of morality that Scanlon calls “what we owe to each other.”

Scanlon’s core test for moral wrongness is this: an action is wrong if it would be prohibited by any principle that no one could reasonably reject. On Scanlon’s formulation, an act is wrong if it would be disallowed by any principle that no one could reasonably reject for general adoption. This makes moral reasons fundamentally relational: they arise from what we owe to each other, including obligations of fidelity, non-harm, fairness, and respect.

Scanlon’s framework is important because it shifts the center of gravity in ethics from abstract principles to interpersonal justifiability. We are not simply asking “what rule produces the best outcomes?” or “what does duty demand?” We are asking: could I justify this action to the person it affects, using reasons they could not reasonably refuse? Contractualism focuses on the standpoint of individual persons, treating each person’s perspective as morally significant rather than allowing it to be overridden by aggregated welfare calculations.

How rational constructivism differs from other ethical theories 🔗

Constructivism vs. moral realism 🔗

Moral realism holds that ethical facts are like facts about chemistry or mathematics – they exist independently of what anyone thinks or agrees upon. Rational constructivism denies this. It does not say there are no moral truths, but it does say those truths are not “out there” awaiting discovery. They are constituted through the outcomes of ideal rational procedures. This makes constructivism especially attractive to thinkers who are skeptical of mysterious, non-natural moral properties, while still wanting to maintain that ethics is more than mere opinion.

Constructivism vs. relativism 🔗

A common misreading is that constructivism collapses into relativism – the view that morality is just whatever a culture happens to believe. This is incorrect. Constructivism requires that principles survive rational scrutiny under idealized conditions. A principle endorsed only because of bias, ignorance, or power imbalance does not pass the test. All constructivists agree that an adequate metaethics should not be totally revisionary; rather, it should be congruent with common understandings of rationality and morality. The standard is rational defensibility, not mere cultural consensus.

Constructivism vs. utilitarianism 🔗

Utilitarianism asks us to maximize overall well-being, even when this requires ignoring the rights or complaints of individuals who happen to be in the minority. Constructivism firmly rejects this aggregative logic. Contractualism does not aggregate, but rather focuses on the standpoint of individual persons. Each person’s reasons matter as such – they cannot simply be outweighed by summing up benefits to others. This gives constructivism a distinctly rights-protective character.

Strengths and challenges 🔗

Rational constructivism has several compelling strengths. It grounds morality in something we can actually engage with – human reason – rather than in mysterious metaphysical entities. It respects autonomy by making moral principles the product of rational agents reasoning together, not impositions from outside. It is also naturally hospitable to moral progress: because principles are constructed through ongoing deliberation, reason appears to have a history, which coincides with the development of practices of tolerance and mutual recognition. This means constructivism can explain how our moral understanding evolves without abandoning the idea of moral truth.

Yet the theory faces genuine challenges. Critics argue that if moral truths are constituted by agreement, then the very standards used to evaluate whether an agreement is “rational” or “fair” must themselves come from somewhere – and this seems to presuppose unconstructed moral norms. There are also practical worries: real human deliberation is never fully ideal. People reason under conditions of inequality, bias, and incomplete information. How close does actual deliberation need to come to the ideal for its outputs to carry moral weight? These remain open and important questions within the field.

Why rational constructivism matters today 🔗

Rational constructivism is not merely a textbook position – it has real implications for how we think about law, democracy, bioethics, and global justice. When democratic societies debate policies on healthcare access, climate change, or economic inequality, they are – at least implicitly – engaged in a constructivist project: trying to arrive at principles that can be justified to all citizens on the basis of shared reason. Rawls’s framework has directly shaped debates about principles of justice for just political institutions, while Scanlon’s contractualism has influenced how philosophers think about global justice, human rights, and structural injustice.

In this sense, rational constructivism is less a complete moral system than a powerful method: a way of asking, with rigor and fairness, what moral principles we can justify to one another when we take each other seriously as rational, equal agents.

What do you think? If moral principles are constructed through rational agreement rather than discovered as pre-existing truths, does that make them more or less binding on us – and why? Is it possible for any real-world deliberation to be “rational enough” to generate genuinely valid moral principles, given the biases and inequalities that shape actual human reasoning?

References

1. https://plato.stanford.edu/entries/constructivism-metaethics/
2. https://www.cambridge.org/core/books/constructivism-in-ethics/4FDD4C85D8987A32755CD530FEC665EE
3. https://plato.stanford.edu/archives/win2024/entries/constructivism-metaethics/
4. https://iep.utm.edu/constructivism-in-metaethics/
5. https://en.wikipedia.org/wiki/Original_position
6. https://plato.stanford.edu/entries/rawls/
7. https://ethicsunwrapped.utexas.edu/glossary/veil-of-ignorance
8. https://plato.stanford.edu/archives/win2017/entries/constructivism-metaethics/
9. https://philopedia.org/schools/contractualism/
10. https://en.wikipedia.org/wiki/T._M._Scanlon
11. https://plato.stanford.edu/entries/contractualism/
12. https://plato.stanford.edu/archives/spr2015/entries/constructivism-metaethics/