John Leslie Mackie

Life and Academic Career

John Leslie Mackie (1917–1981) was an Australian philosopher who became one of the most distinctive figures in twentieth‑century analytic philosophy, especially in ethics and metaphysics. Born in Sydney, he studied at the University of Sydney, where he was influenced by the emerging analytic tradition, and later at Oriel College, Oxford. His early academic work was interrupted by service in the Second World War, after which he resumed his philosophical career.

Mackie held posts at the University of Sydney and the University of Otago (New Zealand) before returning to the United Kingdom. In 1967 he was appointed Wykeham Professor of Logic at the University of Oxford, one of the most prestigious chairs in British philosophy, which he held until his death. At Oxford he was a fellow of New College and an influential teacher, known for his clarity, argumentative precision, and willingness to challenge prevailing orthodoxies, particularly moral realism and theism.

His major books include Ethics: Inventing Right and Wrong (1977), The Cement of the Universe: A Study of Causation (1974), and The Miracle of Theism: Arguments for and against the Existence of God (1982, published posthumously). Mackie died in Oxford in 1981, leaving a body of work that continues to be widely discussed in contemporary philosophy.

Moral Error Theory and the Argument from Queerness

Mackie’s most famous contribution is his moral error theory, developed most fully in Ethics: Inventing Right and Wrong. He begins from what he calls the “argument from relativity”: the wide and persistent disagreement about moral values across cultures and historical periods, even among well‑informed and rational people, suggests that morality is not tracking a set of shared objective facts in the way that, for example, the natural sciences aim to do. Instead, Mackie proposes that variation in moral codes is better explained by different social, psychological, and cultural conditions.

The centerpiece of his view, however, is the “argument from queerness.” Mackie argues that if there were objective moral values—properties of things that make them intrinsically right or wrong—they would be metaphysically queer (ontologically very unlike anything else we know) and epistemically queer (knowable, if at all, in some radically special way). Moral properties, as ordinarily conceived, would have to be intrinsically action‑guiding or motivating, such that to recognize an action as objectively wrong would, by itself, give one a reason not to do it. Mackie contends that positing such intrinsically prescriptive properties is philosophically extravagant.

From these considerations he draws his error‑theoretic conclusion:

• Ordinary moral discourse—claims such as “murder is wrong” or “generosity is good”—purports to state objective facts.
• However, there are no such objective moral facts or properties.
• Therefore, ordinary positive moral judgments are systematically false, even though they are meaningful and important in human life.

This distinguishes Mackie from non‑cognitivists, who treat moral utterances as expressions of attitudes rather than truth‑apt statements, and from subjectivists or relativists, who locate moral truth in individual or cultural attitudes. Mackie is a cognitivist anti‑realist: he grants that moral sentences express propositions but denies that any of those propositions are true.

Mackie does not recommend abandoning morality in practice. Instead, he proposes an “invention” or constructivist understanding: humans create moral systems to serve practical purposes—coordination, cooperation, conflict resolution—rather than discover them as objective features of reality. Moral values, on this view, are human constructions, not objective presences.

His position has generated extensive debate. Proponents of Mackie’s approach claim that it offers a parsimonious explanation of moral disagreement and avoids puzzling commitments about sui generis moral properties. Critics argue that the argument from queerness either mischaracterizes what moral realists are committed to, or else assumes a controversial view about motivation and reasons. Some moral realists develop naturalistic accounts of moral properties, claiming that they can be identified with or grounded in natural facts (for example, facts about well‑being or flourishing), thereby attempting to neutralize the charge of metaphysical queerness. Others challenge Mackie’s assumption that recognizing a moral fact must be intrinsically motivating.

Despite these criticisms, Mackie’s error theory remains a central reference point in contemporary metaethics, shaping discussions of moral realism, expressivism, and constructivism.

Causation, Metaphysics, and Philosophy of Religion

Beyond ethics, Mackie made major contributions to the analysis of causation. In The Cement of the Universe, he develops a detailed account of causal relations in terms of INUS conditions: an event is a cause of another event when it is an Insufficient but Non‑redundant part of an Unnecessary but Sufficient condition. This analysis aims to capture the complex ways in which causes typically operate as elements within larger causal complexes rather than as isolated sufficient conditions.

Mackie’s approach fits within the analytic tradition’s concern with counterfactuals, regularities, and the structure of explanation. It has been influential in both philosophy and legal theory, where questions of causal responsibility are central. Supporters view INUS conditions as a flexible way to model multi‑factor causation; critics question whether the account can handle probabilistic causation or distinguish genuine causes from mere background conditions without circularity.

In metaphysics and philosophy of language, Mackie engaged with issues such as the nature of truth, objectivity, and the relationship between language and reality, often from a broadly empiricist and critical standpoint. His reflections on objectivity in ethics formed part of a wider concern with how value and normativity can be reconciled with a naturalistic outlook.

Mackie’s The Miracle of Theism is a sustained examination of arguments for and against the existence of God. Unlike many earlier critiques of religion, the book systematically surveys cosmological, teleological, ontological, and moral arguments for theism, as well as arguments from religious experience and pragmatic defenses. Mackie carefully reconstructs these arguments in their strongest forms before offering objections, making the work valuable even to theists.

He famously characterizes the success of theism as, in a sense, a “miracle” given what he regards as the limited strength of the arguments in its favor. At the same time, he examines arguments for atheism, such as the problem of evil, and considers whether secular moral and existential outlooks can provide adequate replacements for religious frameworks.

Reactions to The Miracle of Theism divide along familiar lines. Secular philosophers often praise its rigor and fairness in presenting theistic arguments; theistic philosophers frequently accept Mackie’s formulations of their positions but dispute his assessments, offering alternative responses to the problem of evil and revamped versions of classical arguments.

Across ethics, metaphysics, and philosophy of religion, Mackie’s work is unified by a commitment to clarity, logical analysis, and a generally sceptical, naturalistic outlook. His combination of precise argumentation with a readiness to challenge entrenched assumptions has ensured his continuing influence in debates about moral objectivity, the nature of causation, and the rational standing of religious belief.