Brian Edward Leftow

1. Introduction

Brian Edward Leftow (b. 1956) is a leading figure in contemporary analytic philosophy of religion, known especially for systematic work on divine eternity, modal metaphysics, and classical theism. Working primarily within the Anglo-American analytic tradition, he has sought to show that traditional Christian doctrines about God can be articulated with the same precision and ambition as secular metaphysical theories.

A distinctive feature of Leftow’s contribution is the combination of three elements: detailed model-building about God and time; a theistic metaphysics of modality in which truths about possibility and necessity depend on God; and an analytic reconstruction of Aquinas’s metaphysics aimed at making classical theism a live option in contemporary theory choice. Across these areas he engages directly with major non-theistic philosophers of metaphysics and language, presenting theism as a competitor rather than a special-interest discourse.

Leftow’s work is often taken to represent a particularly strong form of divine aseity: not only does God depend on nothing, but even abstract objects and modal truths are ultimately grounded in God’s nature, intellect, and creative activity. His formulations of ET-simultaneity (eternal–temporal simultaneity) and his account of God and Necessity have become standard reference points in debates about God’s relation to time, possible worlds, and necessary truths.

Situated historically in the second generation of analytic philosophers of religion after Alvin Plantinga and Richard Swinburne, Leftow’s writings are widely discussed by both supporters and critics, who dispute the coherence, theological adequacy, and metaphysical costs of his ambitious system but generally treat it as one of the most fully developed contemporary versions of classical theism.

2. Life and Historical Context

Leftow was born in the United States in 1956, placing his intellectual formation amid the late‑twentieth‑century revival of analytic philosophy of religion. After doctoral study at the University of Oxford, where he completed his D.Phil. in 1983, he taught at Fordham University in the 1980s before returning to Oxford as Nolloth Professor of the Philosophy of the Christian Religion in 1993. In 2018 he moved to Rutgers University, joining a large research department heavily focused on analytic metaphysics.

2.1 Career Milestones

2.2 Intellectual Environment

Leftow’s early career coincided with a period in which analytic theism—associated with figures such as Plantinga and Swinburne—reintroduced rigorous discussion of God’s existence and attributes into Anglophone philosophy. Proponents sought to employ modal logic, possible‑worlds semantics, and contemporary metaphysics in the service of classical doctrines.

During his Oxford years, debates about God and time, divine foreknowledge and freedom, and the coherence of theism were particularly prominent. Leftow contributed to and helped shape these discussions, while also interacting with medieval studies and the emerging movement of analytic Thomism.

His move to Rutgers placed his work directly within a broader metaphysical scene shaped by David Lewis–style modal realism, debates over grounding and abstracta, and increasing interest in the metaphysics of religion. This context encouraged the development of his more systematic engagements with modality and the ontology of necessary truths.

3. Intellectual Development

Leftow’s intellectual trajectory can be divided into several overlapping phases, each marked by characteristic topics and interlocutors.

3.1 Early Analytic Theism

In his formative period (late 1970s–mid 1980s), Leftow worked within the framework opened by Plantinga and Swinburne. Early publications explored divine foreknowledge, freedom, and the coherence of divine attributes using modal logic and counterfactuals. The main emphasis was on defending a broadly classical theism against standard objections, rather than on constructing an independent metaphysical system.

3.2 Systematic Work on God and Time

In the 1990s, particularly after assuming the Nolloth Chair, Leftow turned toward building a comprehensive theory of divine eternity and the God–world relation. This period culminated in Time and Eternity (1997), where he developed the ET-simultaneity model. Here, his work became more structurally ambitious, aiming to integrate theology with general metaphysics of time and causation.

3.3 Analytic Thomism and Medieval Engagement

From the late 1990s into the 2000s, Leftow increasingly engaged with Thomas Aquinas and medieval metaphysics, leading to Aquinas on Metaphysics (2004). He adopted and reinterpreted Thomistic notions—such as esse, act and potency, and divine simplicity—within a contemporary analytic idiom. This phase positioned him among key contributors to analytic Thomism, though interpreters differ on how closely his reconstructions follow Aquinas.

3.4 Metaphysics of Modality and System‑Building

In the 2010s, especially with God and Necessity (2012), Leftow’s focus shifted to modal metaphysics, the grounding of possible worlds, and the status of necessary truths. He developed a comprehensive theistic account of modality, linking it to divine ideas and God’s creative capacities. This mature phase integrates earlier work on eternity and classical theism into a broader metaphysical picture in which God underwrites not only the actual world but the entire modal structure within which it is situated.

4. Major Works

Leftow’s major publications develop interconnected themes concerning God, time, metaphysics, and modality. The following overview highlights their central aims and contexts.

4.1 Time and Eternity (1997)

In Time and Eternity, Leftow offers a detailed analysis of divine eternity and the relation between a timeless God and temporal creation. He introduces and defends ET-simultaneity, arguing that God is timeless yet simultaneous with every temporal event. The book systematically assesses rival positions—such as divine temporality or Boethian timelessness without ET-simultaneity—and addresses implications for creation, foreknowledge, and providence.

4.2 Aquinas on Metaphysics (2004)

Aquinas on Metaphysics reconstructs Thomas Aquinas’s metaphysical system in contemporary terms. Leftow examines topics such as esse and essence, substance and accident, causation, and divine simplicity, arguing that Aquinas presents a sophisticated theory of being that can inform current debates. The work functions both as a historical study and as a proposal for how classical theism might be integrated into modern analytic metaphysics.

4.3 God and Necessity (2012)

In God and Necessity, Leftow develops a comprehensive theistic metaphysics of modality. He criticizes secular views such as Lewisian modal realism and various ersatzist theories, proposing instead that possible worlds are grounded in God’s nature, thoughts, and powers. The book elaborates how necessary truths—including logical, mathematical, and metaphysical necessities—depend on what God is and can do.

4.4 Influential Articles and Essays

Beyond these monographs, several articles have been particularly influential:

These pieces extend and refine the system articulated in his books and are widely cited in contemporary debates.

5. Core Ideas: God, Time, and Eternity

Leftow’s work on God and time centers on a distinct conception of divine eternity and its relation to temporal reality.

5.1 Timelessness and ET‑Simultaneity

Leftow defends the claim that God is timeless—lacking temporal location, succession, and change—yet stands in a special relation of ET-simultaneity to every temporal event. On this view, an eternal God is “present” to each moment of time without being earlier or later than any moment.

"

“On my view, an eternal God is simultaneous with every temporal event without sharing our temporal location.”

— Brian Leftow, Time and Eternity

This is sometimes contrasted with more traditional Boethian or Thomistic accounts, which affirm timelessness but leave the mechanism of God–time relations less articulated.

5.2 Time as a Feature of Creation

Leftow treats time as a feature of the created order grounded in God’s timeless creative activity. Time begins with creation; there is no “before” creation in a temporal sense, though God’s timeless act can be said to explain that first moment. He summarizes:

"

“God is not in time, but time is in God’s creative act.”

— Brian Leftow, Time and Eternity

On this model, divine acts that appear temporally successive from a creaturely perspective may all be aspects of a single timeless divine action.

5.3 Comparisons and Critiques

Leftow’s model is often compared with:

Proponents hold that ET-simultaneity reconciles timelessness with real interaction, providence, and knowledge of temporal events. Critics question whether the relation of simultaneity without shared temporal location is intelligible, and whether it preserves genuine responsiveness or change in God’s knowledge and will.

6. Modal Metaphysics and God’s Necessity

Leftow’s modal metaphysics proposes that possibility and necessity ultimately depend on God’s nature and creative capacities. He aims to provide a theistic rival to secular accounts of possible worlds.

6.1 Theistic Grounding of Modality

In God and Necessity, Leftow defends the thesis:

"

“If there are any necessary truths at all, they are necessary because of what God is and what God can do.”

— Brian Leftow, God and Necessity

On this view, possible worlds are not concrete universes (as in Lewis’s modal realism) nor purely abstract sets of propositions. Instead, they are in some way grounded in divine ideas, God’s understanding of how things could be, together with God’s powers to realize those states of affairs. Necessary truths express constraints rooted in God’s essential nature; contingent truths depend on God’s free choices among the possibilities God surveys.

6.2 Comparison with Secular Theories

Proponents of Leftow’s approach see it as securing a robust divine aseity: modal truths do not limit God from “outside” but arise from what God is. Critics worry about circularity (using God to explain modality when divine attributes are themselves modal), and dispute whether this yields the same modal logic as secular accounts.

6.3 God’s Necessity

Leftow holds that God exists necessarily and that many necessary truths concern what God is and cannot fail to be. God’s necessity is not one necessary being among others but the ultimate metaphysical ground of all necessity. Alternative positions include treating God, if he exists, as a contingent being, or proposing non-theistic sources of necessity (such as logical structures or abstract entities). Leftow’s system is designed to contrast with these by making divine necessity explanatorily fundamental.

7. Engagement with Aquinas and Classical Theism

Leftow engages extensively with Thomas Aquinas and the classical theist tradition, aiming to show how its central claims can be formulated and evaluated using contemporary analytic tools.

7.1 Aquinas on Being and God

In Aquinas on Metaphysics, Leftow reconstructs Aquinas’s distinction between esse (act of being) and essentia (essence), emphasizing its implications for the doctrine of God as actus purus (“pure act”). He writes:

"

“For Aquinas, being is not a highest genus but the act that makes every nature to be; to understand this is to see why God must be pure act.”

— Brian Leftow, Aquinas on Metaphysics

On Leftow’s reading, God alone is identical with his act of being, while creatures have their being in a received and dependent way. This shapes his understanding of divine simplicity, aseity, and the Creator–creature distinction.

7.2 Classical Theism in Analytic Dress

Leftow defends a version of classical theism characterized by:

• Divine simplicity (no composition of essence and existence, form and matter, or distinct properties in God)
• Timeless eternity
• Immutability and impassibility in a carefully qualified sense
• Strong aseity, including dependence of abstracta and modal truths on God

He presents this as a systematic metaphysics, not merely a set of historical doctrines. Proponents of analytic Thomism see this work as demonstrating the continuing philosophical viability of Aquinas-inspired views.

7.3 Debates over Interpretation and Development

Scholars diverge on how faithfully Leftow follows Aquinas and classical sources:

Some interpreters view Leftow as a creative developer of classical theism; others regard his project as an analytic system merely inspired by, but not identical with, traditional Thomism.

8. Methodology and Style of Argument

Leftow’s work is characteristically analytic, systematic, and model‑theoretic in style. He combines close conceptual analysis with large‑scale metaphysical construction.

8.1 Model‑Building and Thought Experiments

A recurring method is to construct detailed models of how doctrines might be true, then compare their internal coherence and explanatory power with rival models. In discussions of eternity, the Trinity, or modality, he frequently introduces intricate scenarios (e.g., thought experiments about timelines, causal orders, or divine ideas) to clarify logical possibilities.

This approach aligns his work with broader analytic metaphysics, where the evaluation of candidate “world‑pictures” is central.

8.2 Engagement with Objections

Leftow often structures arguments around systematic engagement with objections. Chapters in Time and Eternity and God and Necessity are organized as sequences of:

1. Presentation of a doctrine or thesis
2. Survey of standard and novel objections
3. Step‑by‑step replies, sometimes involving modifications to the initial position

Supporters regard this as exemplifying rigorous defeater‑defeater methodology. Critics sometimes argue that the resulting positions become highly complex or revisionary.

8.3 Use of Historical Sources

In dealing with Aquinas and classical theism, Leftow reads historical texts through a contemporary metaphysical lens. He tends to translate scholastic concepts into modern categories (e.g., grounding, possible worlds, property theory). Advocates claim this makes classical thought accessible and testable within current debates; detractors worry that it risks anachronism or loss of historical nuance.

8.4 Formal and Logical Tools

Although not primarily a technical logician, Leftow makes extensive use of:

• Modal logic and possible‑worlds semantics
• Distinctions between de re and de dicto modality
• Concepts such as essence, grounding, and dependence

His style is dense and argumentative rather than rhetorical, aiming at clarity of structure even when the metaphysical claims are controversial.

9. Impact on Philosophy of Religion and Metaphysics

Leftow’s influence spans both philosophy of religion narrowly construed and general metaphysics.

9.1 God and Time Debates

His ET‑simultaneity account is widely cited in discussions of divine eternity. Subsequent work on God and time routinely engages with his arguments, either adopting variants of ET‑simultaneity or developing temporalist and hybrid theories partly in response. Supporters see his model as raising the standard of precision in this area; critics use it as a foil for alternative accounts.

9.2 Analytic Thomism and Historical Engagement

Within the movement often called analytic Thomism, Aquinas on Metaphysics helped demonstrate the possibility of integrating medieval metaphysics with contemporary debates about being, causation, and identity. Some Thomists endorse his reconstructions as philosophically fruitful; others use them as a point of contrast to argue for more textually conservative readings.

9.3 Metaphysics of Modality

In modal metaphysics, God and Necessity is one of the most prominent recent defenses of a theistic possible‑worlds theory. It is discussed alongside Lewisian modal realism, Williamson’s necessitism, and various ersatzist views. Even philosophers not sympathetic to theism often cite it as a sophisticated articulation of how theism might underwrite modality.

9.4 Cross‑Disciplinary Effects

Leftow’s work has also influenced systematic theology, especially in discussions of the Trinity, Incarnation, and divine attributes, by providing detailed metaphysical frameworks that theologians may appropriate or contest. His writings feature in handbooks and graduate syllabi, shaping how new generations encounter classical theism within analytic philosophy.

10. Legacy and Historical Significance

Although Leftow’s career is ongoing, commentators already situate his work within the broader history of analytic philosophy of religion.

10.1 Place in the Analytic Theist Tradition

Leftow is often seen as part of the second major wave of analytic theism, following pioneers like Plantinga and Swinburne. Whereas earlier figures focused heavily on arguments for God’s existence and the coherence of individual attributes, Leftow’s work is frequently characterized as a turn toward large‑scale system‑building, integrating doctrines of God, time, and modality into a unified metaphysical picture.

10.2 Classical Theism in Contemporary Debate

Historically, his writings contribute to the rehabilitation of classical theism—especially Thomistic themes—within mainstream analytic discourse. Supporters argue that he has shown classical doctrines can compete with leading secular theories in sophistication and explanatory scope. Others regard his system as illustrating both the possibilities and the limits of importing pre‑modern theology into late‑modern metaphysics.

10.3 Ongoing Reception and Controversies

Leftow’s positions on timeless eternity, divine simplicity, and the grounding of modality remain active sites of debate. Some philosophers and theologians treat his work as a benchmark that any alternative account must address. Critics contend that the complexity of his models and their strong commitments (e.g., to timelessness and maximal aseity) reveal tensions within classical theism when subjected to contemporary analytic scrutiny.

10.4 Prospects for Future Assessment

Future historical assessments are likely to consider:

Even as interpretations differ, Leftow is widely regarded as a central figure in the late‑20th‑ and early‑21st‑century attempt to articulate a philosophically rigorous and systematically ambitious version of classical theism.