---
title: Foundations of Ethics
section-id: ethics
sort: 100
author: Prof. James Okafor
created: 2026-02-17 09:00
modified: 2026-03-25 10:00
language: en
description: The major metaethical positions and the question of the objectivity of moral claims.
---

# Foundations of Ethics

Ethics is the philosophical study of how we ought to live and what we ought to do. Before examining the major ethical theories—consequentialism, deontology, virtue ethics—it is worth asking a prior question: what kind of claims are moral claims? Are they objectively true or false? Do they describe features of reality, or express attitudes, or prescribe conduct?

## Metaethics

**Metaethics** is the study of the nature and status of moral claims, distinct from **normative ethics** (which theories of morality are correct) and **applied ethics** (how to act in particular situations).

### Moral Realism
Moral realism holds that there are objective moral facts, independent of what anyone believes or feels. ‘Torture is wrong’ is objectively true (if it is true) in the same way that ‘water is H₂O’ is objectively true. Moral realism captures the common intuition that moral disagreement is genuinely about something: both parties cannot be right.

Varieties of moral realism include:
- **Naturalism**: moral properties are natural properties (e.g., wellbeing, flourishing). Moral facts are a kind of natural fact.
- **Non-naturalism**: moral properties are sui generis, not reducible to natural ones. G.E. Moore’s ‘goodness’ is indefinable in natural terms.
- **Cornell realism**: moral properties are real but not reducible; knowledge of them comes through ordinary perception and reasoning.

### Expressivism
Expressivists deny that moral claims express beliefs with truth conditions. ‘Torture is wrong’ does not describe a fact; it expresses an attitude of disapproval or prescribes against torture. A.J. Ayer’s **emotivism** held that moral sentences are expressions of emotion, not propositions at all.

More sophisticated expressivist views (**quasi-realism**, Simon Blackburn) try to explain how moral discourse can function as if it were truth-apt—how we can speak of moral truths and moral knowledge—without positing moral facts.

### Constructivism
Constructivists hold that moral facts are constructed from the standpoint of rational agents under certain idealised conditions. John Rawls argued that principles of justice are those that rational agents would agree to from behind a **veil of ignorance** (not knowing their place in society, their natural advantages, or their conception of the good). Moral facts are not independent of us but are what we would endorse under ideal conditions of impartiality and rationality.

### Error Theory
J.L. Mackie argued that moral claims purport to describe objective moral facts, but there are no such facts. All moral claims are therefore false. We systematically make an error when we make moral judgements. Error theory is realist in its analysis of what moral claims mean but anti-realist in its metaphysics.

## The Is-Ought Gap

Hume famously observed that arguments in moral philosophy often move from claims about what is the case to claims about what ought to be the case, without justifying the transition. This **is-ought gap** (or **Hume’s guillotine**) suggests that no set of purely descriptive facts entails a normative conclusion without an additional normative premise.

G.E. Moore formalised a related point as the **naturalistic fallacy**: defining moral properties in natural terms and then arguing for moral conclusions from natural facts commits a fallacy. Even if happiness is the only thing desired for its own sake (a natural fact), it does not follow without further argument that happiness is the only thing good in itself.

## Moral Disagreement

Moral disagreement across cultures and individuals is sometimes cited as evidence against moral realism. If there were objective moral facts, we would expect convergence rather than persistent disagreement.

Moral realists have several responses. Disagreement exists in science and history without undermining the objectivity of those domains. Much apparent moral disagreement reduces to disagreement about non-moral facts (e.g., whether a foetus has morally relevant interests). And the content of moral disagreement has converged over time in some respects: most people and cultures no longer endorse slavery or torture of the innocent as acceptable.

## Summary

- Moral realism holds that there are objective moral facts; varieties include naturalism, non-naturalism, and Cornell realism
- Expressivism holds that moral claims express attitudes rather than describe facts
- Constructivism holds that moral facts are constructed by rational agents under idealised conditions
- Error theory holds that moral claims purport to state facts but all are false
- Hume’s is-ought gap and Moore’s naturalistic fallacy pose challenges for deriving moral conclusions from non-moral premises
