Oxford University · Philosophy of Religion

Dr. Leo Vassiliou

Senior Research Fellow · Philosopher of Religion
Natural Theologian · Apologist · Author

Dedicated to the most consequential question the human mind can entertain: whether God exists. Deploying the sharpest tools of analytic philosophy — modal logic, Bayesian epistemology, philosophy of cosmology — in service of that ancient question.

Leo Vassiliou
D.Phil. Oxford · Senior Research Fellow
2036
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0Books Published
0Peer-Reviewed Articles
0Public Debates
0Million Engine Users
0Years at Oxford
Kalām Cosmological Argument · Fine-Tuning Argument · Modal Ontological Argument · Moral Argument · Leibnizian Contingency · Minimal Facts — Resurrection · Bayesian Natural Theology · Philosophy of Religion · Analytic Theology · Kalām Cosmological Argument · Fine-Tuning Argument · Modal Ontological Argument · Moral Argument · Leibnizian Contingency · Minimal Facts — Resurrection · Bayesian Natural Theology · Philosophy of Religion · Analytic Theology ·

The Mind Behind
the Argument

Leo Vassiliou is one of the foremost voices in contemporary analytic philosophy of religion. His work is characterised by a refusal to separate rigorous philosophical method from genuine theological conviction — deploying modal logic, Bayesian epistemology, and philosophy of cosmology in the service of natural theology's oldest and deepest question.

Educated at the University of York (BA, First Class) and Oxford (M.Phil. and D.Phil.), his doctoral dissertation — Probabilistic Theism and the Cumulative Case — was awarded the Sheppard Prize. He has held a Senior Research Fellowship at Wycliffe Hall, Oxford, since 2034, following a postdoctoral residency at Notre Dame's Center for Philosophy of Religion.

"The question of God's existence is not merely a religious question. It is the question on which every other question about meaning, morality and cosmos ultimately depends."
Natural Theology Bayesian Epistemology Modal Metaphysics Philosophy of Cosmology Christian Apologetics Early Christology Divine Attributes Resurrection Historiography Analytic Theology Philosophy of Science
Published Works

Six Books.
One Question.

I · 2034
Constructing God
Philosophical Blueprints of The Architect
The cumulative case for classical theism, reconstructed from first principles using the tools of analytic philosophy and contemporary cosmology.
Oxford University Press
II · 2035
Deus Renatus Est
The Rebirth of God in Analytic Thought
A survey and defence of the renaissance of theism in twentieth and twenty-first century analytic philosophy, from Plantinga to the present.
Eerdmans Publishing
III · 2033
The Secular Sin
Finding Meaning in a Meaningless Landscape
A philosophical and pastoral examination of the nihilistic consequences of atheism and the failure of secular frameworks to ground ultimate meaning.
InterVarsity Academic
IV · 2031
Growing Up in Nineveh
Faith, Doubt and the Examined Life
A memoir of intellectual and spiritual formation — the journey from curiosity to conviction, doubt to certainty, and the philosophical life as vocation.
SPCK Publishing
V · 2032
The Voice of One Calling in The Wilderness
Sermons at the Edge of Reason
Collected sermons and pastoral addresses — the apologist speaking not to the academy but to the congregation, the sceptic, the seeker.
Crossway

The Theism
Probability
Engine

The world's first interactive Bayesian framework for evaluating arguments for the existence of God. Users input their credences across the major theistic arguments and receive a calculated posterior probability distribution across worldviews — from naturalism to Christian theism.

Built at the intersection of philosophy, probabilistic reasoning and software engineering — a project that began in a first-year computer science dorm room and became one of the most visited resources in online apologetics.

2.4M
Users Worldwide
18
Arguments Modelled
34
Academic Citations
Interactive demo — adjust your credences
Posterior worldview probabilities
Christian Theism
Most probable worldview given your inputs

"Vassiliou has done for the 21st century what Plantinga did for the 20th — given theistic belief not merely a defence, but a philosophical architecture."

— Prof. J. R. Hartley, Notre Dame · Faith & Philosophy, 2035

Education

2030 – 2033
D.Phil. in Philosophy
University of Oxford
Dissertation: Probabilistic Theism and the Cumulative Case. Awarded the Sheppard Prize. Supervised by Prof. R. T. Forster.
2028 – 2030
M.Phil. in Philosophy
University of Oxford
Modal metaphysics and philosophy of religion. Distinction.
2025 – 2028
B.A. Philosophy — First Class Honours
University of York
Top of cohort. Dissertation on the Kalām Argument and the beginning of the universe.

Career

2034 – Present
Senior Research Fellow
Wycliffe Hall, University of Oxford
Theology and Philosophy of Religion. Graduate seminars in natural theology and Bayesian epistemology of religion.
2033 – 2034
Postdoctoral Research Associate
Notre Dame Center for Philosophy of Religion
Collaborated on the Theism and Science project. Visiting lecturer in analytic philosophy of religion.
2026 – Present
Founder · Theism Probability Engine
theismprobability.com
Founded as a student project. Now the world's most-visited Bayesian natural theology tool, with 2.4 million users.
Natural Theology
Developing and defending the strongest versions of cosmological, teleological, ontological and axiological arguments through rigorous analytic method. The cumulative case approach is central to all of Leo's work.
Bayesian Epistemology
Formalising the evidential weight of theistic arguments using probabilistic frameworks. Making explicit what has always been implicit in cumulative case reasoning — and quantifying it.
Christian Apologetics
The historical case for the Resurrection via the Minimal Facts method, early Christology, the reliability of the New Testament, and the evidential case for classical Christian belief specifically.
Speaking

Selected Talks
& Debates

Debate · 2035
"Does God Exist?" — Vassiliou vs. Prof. A. Flanagan
Oxford Union · 1,200 in attendance
Lecture · 2034
The Kalām Argument and Quantum Cosmology
Notre Dame Philosophy of Religion Conference
Debate · 2033
"Is Faith Rational?" — Vassiliou vs. Prof. D. Chen
Cambridge University · Recorded · 4M views
Keynote · 2035
Bayesian Natural Theology and the New Apologetics
Evangelical Philosophical Society Annual Meeting
Sermon · 2032
The Voice of One Calling — on Intellectual Courage
Oxford University Church of St Mary the Virgin
Podcast · Recurring
Reasonable Faith UK — Regular Guest
In the tradition of William Lane Craig's global ministry

Let's Talk About
the Big Questions

Available for speaking engagements, public debates, academic collaboration, media appearances, and questions about the Theism Probability Engine.

Quick Reference
LocationOxford, United Kingdom
Current roleSenior Research Fellow
SpecialisationPhilosophy of Religion
Books published5 (+ 1 forthcoming)
Journal articles22 peer-reviewed
Public debates40+ worldwide
LanguagesEnglish · Greek · Latin (reading)
Open toLectures · Debates · Media