What is the difference between moral realism, subjectivism, and constructivism in contemporary meta-ethics?

Moral realism, subjectivism, and constructivism are three major schools in contemporary meta-ethics that differ fundamentally in their understanding of the nature and existence of moral truths. Understanding these three positions is necessary for comprehending contemporary philosophical debate about the foundation of ethics and its relation to the question of God.

Inadequate responses to be avoided

From some believers:

"Moral realism is the only acceptable religious position." Classificatory error. Many contemporary believing philosophers adopt constructivism (such as Robert Adams in some of his writings) or even forms of modified subjectivism. The automatic linking of faith and moral realism is harmful oversimplification.

"Subjectivism and constructivism inevitably lead to absolute moral relativism." Inaccurate. Kantian constructivism, for example, seeks to build objective ethics from practical reason, and modified subjectivism among some philosophers attempts to preserve a degree of objectivity. Distinguishing between positions requires greater precision.

From some naturalists:

"Moral realism requires belief in God." Historical and philosophical error. Many atheist philosophers adopt moral realism (Derek Parfit, Thomas Nagel, David Enoch). Moral realism is a religiously neutral meta-ethical position.

"Constructivism is the only coherent scientific position." Exaggerated claim. Constructivism faces serious philosophical challenges (the problem of arbitrariness in starting points, the problem of moral obligation). There is no philosophical consensus on its superiority over alternatives.

Why these responses are inadequate

They share in confusing levels of discussion: meta-ethics (nature of ethics), normative ethics (content of ethics), and applied ethics. They also confuse meta-ethical positions with religious or secular commitments.

Moral Realism

Moral realism affirms three theses:
1. Moral judgments express beliefs capable of truth and falsehood (cognitivism)
2. Some of these judgments are actually true
3. Their truth is independent of human opinions or attitudes

Example: "Torture for pleasure is wrong" is not merely an expression of feeling or cultural position, but an objective truth like "Water is H₂O." Even if all humans believed torture for pleasure was acceptable, it would remain wrong.

Types of moral realism:

- Naturalistic realism (Peter Railton, David Brink): Moral facts are natural facts. "Good" can be reduced to facts about the welfare of conscious beings or social cohesion.

- Non-naturalistic realism (Derek Parfit, David Enoch): Moral facts are non-natural facts, existing independently of the physical world. Moral "ought" cannot be reduced to descriptive facts.

- Theological realism (Robert Adams in some works): Moral facts are grounded in God's nature or commands, but remain objective and independent of human opinions.

Strength: Explains our strong intuition that some actions (like genocide) are objectively wrong, regardless of opinions.

Weakness: Difficulty explaining how we know these moral facts (problem of moral epistemology), and difficulty explaining their place in a natural world (if non-naturalistic).

Moral Subjectivism

Subjectivism denies the existence of objective moral facts. Moral judgments express only subjective positions — feelings, desires, or personal commitments.

Types of subjectivism:

- Simple emotivism (A.J. Ayer): "Murder is wrong" means only "Boo to murder!" — an emotional expression carrying no cognitive content.

- Sophisticated expressivism (Simon Blackburn, Allan Gibbard): Moral judgments express complex attitudes capable of rational justification, but remain subjective in essence.

- Error theory (J.L. Mackie): Moral judgments claim objectivity, but are all false because objective moral facts don't exist.

Strength: Avoids the metaphysical problems of realism (where do moral facts exist?). Explains moral diversity between cultures.

Weakness: Conflicts with our strong intuition that some moral judgments are objective. Difficulty explaining serious moral debate (if it's all subjective, what's the point of arguing?).

Moral Constructivism

Constructivism is a middle position: moral facts exist, but are "constructed" from rational procedures or social agreements, not existing independently.

Types of constructivism:

- Kantian constructivism (Christine Korsgaard, Onora O'Neill): Moral facts are constructed from requirements of practical reason. What can be universally legislated from the perspective of a rational agent becomes moral truth.

- Humean constructivism (Sharon Street): Moral facts are constructed from the starting point of agents' actual values, through consistency and coherence.

- Contractualist constructivism (John Rawls in constructivist interpretation, T.M. Scanlon): Moral facts are constructed from principles that rational agents could agree upon under appropriate circumstances.

Strength: Attempts to combine objectivity (against pure subjectivism) and intelligibility (against mysterious realism). Links ethics to human practical reason.

Weakness: Problem of starting point (why these principles and not others?). Tension between claiming objectivity and dependence on human construction.

Precise methodological differences

The basic difference lies in answering the question: "What makes a moral judgment true?"

- Realist: Correspondence to an independently existing moral fact
- Subjectivist: Truthful expression of the agent's position
- Constructivist: Correct derivation from an appropriate constructive procedure

Illustrative example: "Promises ought to be kept"

- Realist interpretation: This is correct because it corresponds to an objective moral fact about the nature of promises
- Subjectivist interpretation: This expresses my position (or societal position) toward promises
- Constructivist interpretation: This is derived from a rationally justifiable principle (like Kant's golden rule)

Overlaps and hybrid positions

Some philosophers adopt hybrid positions:

- Quasi-realism (Simon Blackburn): Subjectivist in foundation, but mimics realist language and practices
- Realist constructivism (some readings of Scanlon): The constructive procedure reveals pre-existing moral facts
- Response-dependence (David Wiggins): Objective moral facts but dependent on appropriate human responses

Relationship to the question of God

The common error is automatic linking:
- Realism = religious position
- Subjectivism/constructivism = secular position

Reality is more complex:
- Atheist realists: Parfit, Nagel, Enoch
- Believing constructivists: some readings of Ashʿarite ethics
- Believers who see theological realism as the best explanation for moral realism (William Craig)

Where we stand in this debate today

According to the PhilPapers 2020 survey:
- Realism: 62%
- Anti-realism (includes subjectivism, constructivism, and others): 38%

The debate is very active, with developments such as:
- "Robust realism" (David Enoch) which acknowledges realism's difficulties but sees it as the best alternative
- "Evolved constructivism" which attempts to integrate insights from evolutionary psychology
- Attempts to link meta-ethics with philosophy of mind and language

The sound position, according to the method of "rational preponderance" (rajḥān ʿaqlī): each position has its strengths and weaknesses. Choice depends on weighing theoretical costs. Realism explains objectivity but at metaphysical cost. Subjectivism avoids the cost but at the price of objectivity. Constructivism attempts a middle position with its own challenges.