One of Baghdad's most celebrated teachers walked out of his lecture hall in 1095 and did not come back. Abu Hamid al-Ghazali had lost his voice, his appetite and, for a while, his certainty. He had read every school of thought he could find and could no longer say how he knew anything at all. His recovery, he wrote later, came 'not by arranging proofs' but by 'a light which God cast into the breast'.
Al-Ghazali was also one of the sharpest arguers in history. That tension runs through everything below. Some of the greatest minds in Greek, Muslim, Jewish and Christian history tried to show by reason alone that there must be a First Cause. Others, just as great, said reason cannot get there. Almost all of them agreed on one thing: the question is worth asking.
“Or were they created out of naught? Or are they the creators? Or did they create the heavens and the earth? Nay, but they are sure of nothing!”
Qur'an 52:35-36 · Pickthall (1930)
These short questions come from an early Meccan chapter. They are often quoted as the seed of the Muslim philosophical argument from causes: everything that begins has a cause, so what caused the world? The Qur'an puts them as questions, not as a syllogism, and leaves the listener to answer.
What the thinkers said
Plato (about 428–348 BCE) pictured the Form of the Good as like the sun: the source that makes everything else both exist and be knowable (Republic, Book 6). In the Timaeus a divine craftsman shapes the world because he is good and 'free from jealousy', wanting all things to be as like himself as they could be. His student Aristotle (384–322 BCE) argued that motion and change in the universe need an ultimate source that is not itself moved: the Unmoved Mover, pure activity, 'thought thinking itself', which moves the heavens not by pushing but 'as the object of love' (Metaphysics, Book 12).
Ibn Sina, known in Europe as Avicenna (980–1037), born near Bukhara, gave the argument a new shape. Everything we meet is 'possible' in itself: it could exist or not, and needs something else to make it actual. A chain of merely possible things cannot explain itself, however long it is. So there must be a Necessary Existent (wājib al-wujūd), whose very nature is to exist. Muslim, Jewish and Christian philosophers argued over this idea for centuries. Al-Ghazali (1058–1111) attacked parts of it in The Incoherence of the Philosophers, but defended another argument, which the Muslim theologians, the mutakallimūn, had developed: whatever begins to exist has a cause; the universe began to exist; so it has a cause. This is the kalām argument, named after the Arabic word for theology. The Jewish scholar Saadia Gaon (882–942) led the academy of Sura near Baghdad. Before Ibn Sina was born, Saadia had already used arguments of this kind in The Book of Beliefs and Opinions to show that the world was created from nothing.
Moses Maimonides (1138–1204), born in Córdoba and later a court physician in Cairo, wrote The Guide for the Perplexed in Arabic. He accepted proofs from motion, but insisted that we can say what God is not more truly than what God is. 'By each additional negative attribute,' he wrote, 'you advance toward the knowledge of God.' Thomas Aquinas (1225–1274), an Italian Dominican friar who read Avicenna, al-Ghazali and Maimonides closely, set out his famous Five Ways in the Summa Theologiae: from motion, from causes, from things that might not exist, from degrees of goodness, and from the order of nature. Each ends with the words 'and this everyone understands to be God'.
Then came the critics. The Scottish philosopher David Hume, in his Dialogues Concerning Natural Religion (published in 1779, after his death), asked whether a world full of suffering looked like the work of a good designer, and whether an argument from the world could ever reach a single, infinite, perfect God rather than something smaller. The German philosopher Immanuel Kant, in the Critique of Pure Reason (1781), argued that pure reason cannot reach beyond experience, so neither proofs nor disproofs of God succeed. He called existence 'not a real predicate'. Yet Kant said the argument from the order of nature 'always deserves to be mentioned with respect', and he wrote that two things filled his mind with 'admiration and awe': 'the starry heavens above me and the moral law within me'.
The debate is alive. In the 1970s the American philosopher William Lane Craig revived the kalām argument, citing the Big Bang. Physicists and philosophers such as Sean Carroll reply that our science cannot yet say whether 'the universe began' in the sense the argument needs. In the large 2020 PhilPapers survey of professional philosophers, about two-thirds leaned towards atheism and about one in five towards theism. Among specialists in the philosophy of religion, the balance was reversed. Clever people disagree. That itself is worth noticing.
This site's position is simple: wonder, not proof. These arguments are not a machine for producing faith, and no tradition here says they are. They are an invitation to take the oldest question seriously: why is there something, and not nothing?
What each faith says
Judaism
“And God said unto Moses: 'I AM THAT I AM'; and He said: 'Thus shalt thou say unto the children of Israel: I AM hath sent me unto you.'”
Exodus 3:14 · JPS 1917
Jewish thought holds two instincts in tension. Maimonides placed philosophy at the heart of faith: the very first of his Thirteen Principles is to know that there is a First Being who brought all things into existence. His Guide shaped Jewish, Christian and Muslim thinking for centuries.
Judah Halevi, a generation earlier, warned that the God reached by argument is not yet the God who spoke at Sinai. Jews have kept both voices. The Torah's own description of God is not an argument but a name: when Moses asks who is sending him, God answers 'I AM THAT I AM' (Exodus 3:14). Philosophers from Maimonides to Aquinas read this as the One whose very being is to exist.
Christianity
“By faith, we understand that the universe has been framed by the word of God, so that what is seen has not been made out of things which are visible.”
Hebrews 11:3 · WEB
The Catholic tradition has long held that reason can know God exists, while faith knows who God is. Aquinas built the Five Ways on Aristotle and on his Muslim and Jewish predecessors, then spent thousands of pages on what reason alone cannot reach, such as the Trinity, which Christians believe is one God in three Persons: Father, Son and Holy Spirit.
Other Christians have been wary. In 1654 the mathematician Blaise Pascal had an overwhelming experience of God and sewed a note of it into his coat. It begins: 'God of Abraham, God of Isaac, God of Jacob, not of the philosophers and scholars.' The Letter to the Hebrews says that the universe was framed 'by the word of God', and that this is understood 'by faith'. Christians today range from those who build careful arguments to those who think the arguments miss the point.
Islam
“When the night grew dark upon him he beheld a star. He said: This is my Lord. But when it set, he said: I love not things that set.”
Qur'an 6:76 · Pickthall (1930)
The Qur'an repeatedly invites reasoning. It tells how Abraham (peace be upon him) watched a star, the moon and then the sun set, and each time said, 'I do not love things that set', before turning to 'Lo! I have turned my face toward Him Who created the heavens and the earth, as one by nature upright, and I am not of the idolaters.' (6:76-79, Pickthall). Muslim theologians and philosophers, from al-Kindi and al-Farabi to Ibn Sina, Ibn Rushd and al-Ghazali, built whole schools of thought on such passages.
Many Muslim scholars also taught that argument has limits. Al-Ghazali's own story ends not with a syllogism but with a light 'cast into the breast'. The Qur'an says, 'Vision comprehendeth Him not, but He comprehendeth (all) vision. He is the Subtile, the Aware.' (6:103, Pickthall), and describes God as having 'The Creator of the heavens and the earth. He hath made for you pairs of yourselves, and of the cattle also pairs, whereby He multiplieth you. Naught is as His likeness; and He is the Hearer, the Seer.' (42:11, Pickthall). For many Muslims, reason opens the door; the Names of God show who is on the other side.
Without religion
“Roughly speaking, the word humanist has come to mean someone who trusts to the scientific method when it comes to understanding how the universe works”
Humanists UK, ‘What is humanism?’ · original English
Non-religious philosophers are part of this conversation, not outsiders to it. David Hume, the Scottish sceptic, wrote his Dialogues as a conversation in which no speaker simply wins. Today the Australian philosopher Graham Oppy, an atheist, takes a different line. In Arguing about Gods (2006) he argues that none of the arguments, for God or against, should move a reasonable person who does not already agree. The philosopher A. C. Grayling, a vice-president of Humanists UK, set out a non-religious case in The God Argument (2013).
Many non-religious people share the philosophers' starting wonder: why is there anything at all? The 2020 PhilPapers survey found that most professional philosophers lean towards atheism. Non-religious philosophers themselves are quick to add that this is not a verdict. It is a reminder that careful minds look hard at these arguments and still differ.
Same and different
The three faiths share a remarkable story: Greek philosophy passed through Muslim Baghdad and Persia, into Jewish Córdoba and Cairo, and on to Christian Paris and Naples. Ibn Sina, Maimonides and Aquinas read one another's ideas and argued about them. All three traditions agree that reason can point to a Creator and that it cannot exhaust Him. They differ on what reason is pointing towards: for Jews, the God of the covenant at Sinai; for Christians, the God revealed in Christ; for Muslims, the One who has 'nothing like Him' and is known through His Names. Non-religious philosophers took part in the same conversation, and many found the arguments unpersuasive. They belong in this story too.
A moment to reflect
- Do you think a good argument can lead someone to God, or does it only clear the way?
- Which objection on this page do you find strongest? Which reply?
- Is there a difference, for you, between thinking about life's biggest questions and feeling them?
- What, if anything, fills you with what Kant called 'admiration and awe'?
Watch
Aquinas & the Cosmological Arguments: Crash Course Philosophy #10 · CrashCoursePlays on “Did the universe have a beginning, and does it need a cause?” →A quick, fair introduction to Aquinas and the cosmological arguments, including objections.
Ibn Sina (Avicenna)'s Proof of God's Existence by Dr. Khalil Andani · Dr. Khalil Andani: Thinking IslamPlays on “Did the universe have a beginning, and does it need a cause?” →A Muslim scholar of philosophy explains Ibn Sina's argument from the Necessary Existent.
The life and thought of al-Ghazali, from crisis to his great revival of the religious sciences.
Three minutes on Aristotle's Unmoved Mover.
The design argument and Hume's challenge to it, explained plainly.
Do it together
Give each group one thinker from this page on a card. Each group explains its thinker's idea in two minutes to the others, and one person plays Hume or Kant in reply.
On a clear evening watch a star, the moon and, next morning, the sunrise and sunset. Read Qur'an 6:76-79 together and talk about what does not 'set'.
Ibn Rushd and Maimonides were both born in Córdoba within a few years of each other. Host an evening reading a short passage from each, with food from Andalusian tradition, and talk about learning across faiths.
Jewish study has long been done in chavruta, ‘companionship’: two people read a text aloud together and argue over it, line by line. Pair up across faiths and none, take one paragraph from this page, and read it the chavruta way.
Visit Hereford Cathedral's Chained Library, where medieval books of theology and philosophy are still chained to their shelves, or your nearest cathedral library. Ask what the monks and canons were reading, and why they guarded it so carefully.
Go deeper
- Ibn Sina's Metaphysics (Stanford Encyclopedia of Philosophy) · article
- Al-Ghazali (Stanford Encyclopedia of Philosophy) · article
- Maimonides, Guide for the Perplexed I:59 on Sefaria · scripture
- Aquinas, Summa Theologiae I, q.2 a.3 (New Advent) · article
- Cosmological Argument (Stanford Encyclopedia of Philosophy) · article
- Why is there something rather than nothing? (on this site) · article
- Saadya [Saadiah] Gaon (Stanford Encyclopedia of Philosophy) · article
- What is humanism? (Humanists UK) · article
Sources (10)
- Plato's Good like the sun; Timaeus craftsman free from jealousy: Plato, Republic 508-509; Timaeus 29e (Jowett translation)
- Aristotle's Unmoved Mover, moves as object of love, thought thinking itself: Aristotle, Metaphysics XII.7 and 9 (Ross translation)
- Ibn Sina's Necessary Existent: Stanford Encyclopedia of Philosophy, 'Ibn Sina's Metaphysics'
- Al-Ghazali's crisis of 1095 and 'light cast into the breast': Stanford Encyclopedia of Philosophy, 'al-Ghazali'
- Maimonides on negative attributes: Guide for the Perplexed I:58-59, Friedländer translation 1903 (Sefaria)
- Aquinas's Five Ways, 'this everyone understands to be God': Summa Theologiae I q.2 a.3 (New Advent)
- Hume's Dialogues (1779) and Kant's critique; 'deserves to be mentioned with respect': Stanford Encyclopedia of Philosophy, 'Cosmological Argument' and 'Teleological Arguments'
- Kant: starry heavens and moral law: Kant, Critique of Practical Reason, Conclusion (Abbott translation)
- PhilPapers 2020: about two-thirds atheism, about one in five theism: Bourget and Chalmers, PhilPapers Survey 2020
- Pascal's Memorial, 1654: Encyclopaedia Britannica, 'Blaise Pascal'