In the 1090s, in Baghdad, a man at the peak of his career wrote a book against philosophers. Al-Ghazālī held the leading teaching post of his day. He accused the Greek-trained thinkers of his own world of three errors serious enough to count as unbelief, and he chose his examples so that you could test them in a kitchen: the cotton and the flame. Everyone says the fire burns the cotton. What have you actually seen?
About eighty-five years later, a judge in Córdoba, Ibn Rushd, wrote the reply. A few centuries after that, in Mexico City's convent of San Jerónimo, Sor Juana wrote a letter defending a woman's right to study. In 1550 in Valladolid, in Spain, two men argued before judges over whether the people of the Americas were "natural slaves". In the Ethiopian highlands, a man who had fled persecution and hidden in a cave reasoned his way to a God of reason and to the equality of all people.
This piece follows the arguments, not the biographies. It also tries to be fair to religion: several of these thinkers were devout, some were charged with unbelief, and their reasoning does not depend on whether you share their faith.
In the ninth century the Abbasid court in Baghdad paid for a vast translation of Greek science and philosophy into Arabic. Out of it came falsafa, the Arabic word for philosophy in the Greek manner, as distinct from kalām, the dialectical theology that defended Islamic doctrine by argument. Al-Kindī (c. 801–873) is called the first philosopher of the Arabs; he argued that the world cannot have existed for an infinite past, because an actual infinity cannot be completed by successive addition. Al-Fārābī (c. 872–950), known as the "Second Teacher" after Aristotle, built on logic and wrote on the ideal city and on how a prophet and a philosopher can both grasp truth.
The most original of them is Ibn Sīnā, known in Latin as Avicenna (980–1037). He is famous for medicine (the Canon, finished around 1025) and for two arguments. The first is the "flying" or "floating man", a thought experiment about the soul. Imagine you are created fully formed, suspended in empty air, eyes covered, limbs apart so that you touch nothing and feel nothing.
The step doing the work is 3, and objectors go for it. That I can conceive of myself without a body does not show that I could exist without one (a person can think of water without thinking of H₂O). Avicenna replied that the experiment is meant to make you notice a direct self-awareness that does not come through the senses, not to run a proof. Descartes's "I think" argument came six centuries later, and whether Avicenna influenced it is debated.
A paraphrase of the argument in Avicenna's Kitāb al-Shifā' ("The Healing"), On the Soul, with the standard objection and reply added.
Without JavaScript: imagine a person made fully formed, floating with no sensation. She would still be aware of herself, though not of any body, so (says Avicenna) the self is not the body. Objection: being able to conceive it does not show it could happen.
His second argument concerns God, and it is a good example of how an argument can be examined without anyone's faith being the test. Avicenna separates a thing's essence (what it is) from its existence (that it is). For anything whose essence does not include existence, existence has to come from something else. A chain of such things must end in a being whose essence is its existence, which he calls the Necessary Existent. Critics ask why the chain must end, whether "existence" is the kind of property that can be part of an essence at all, and whether such a being must be a god or a person. Believers reply that the argument gets the structure of the world right, and defenders and critics alike still use it as a model of how a metaphysical argument is built.
Al-Ghazālī (1058–1111) taught at the Niẓāmiyya in Baghdad, then went through a crisis in 1095, left his post and travelled, and came back to write. His Incoherence of the Philosophers (Tahāfut al-falāsifa, c. 1095) attacks the philosophers, mainly Avicenna and al-Fārābī, on twenty points. Three, he said, put them beyond the pale: that the world is eternal, that God knows only universals and not particulars, and that bodies will not be resurrected. On the rest he thought they were wrong but not unbelievers.
The part that interests philosophers today is the seventeenth discussion, on causation. The philosophers held that causes necessitate their effects: the fire's nature makes the cotton burn. Al-Ghazālī's argument is about evidence:
His own positive view is close to occasionalism, the Ash'arite kalām position that God directly brings about every event on the occasion of the preceding one. This is not a scientific scepticism: it protects the possibility of miracles. But the argument stands apart from the use he made of it. In 1739 David Hume made a similar point about "constant conjunction" from the opposite direction, to cast doubt on our grip on necessity, with no God in the picture. Whether Hume knew of al-Ghazālī is not established.
Four positions on one scene. The fourth (Ibn Rushd) is taken up in the next section.
Without JavaScript: we observe cotton burning after contact with fire (Ghazālī: "with", not "by"). He concludes necessity is not shown; God can act otherwise. Hume (1739): we see conjunction, not necessity. Ibn Rushd: denying that natures cause their effects destroys knowledge.
Al-Ghazālī also gave a famous argument for God's existence, the kalām cosmological argument: whatever begins to exist has a cause; the world began to exist; so the world has a cause. Both premises are disputed. Some philosophers and physicists question whether the first premise applies to the universe as a whole; others question whether the universe had a beginning in the relevant sense, or whether an infinite past is impossible; and many theists think the argument works while others prefer different ones. Present-day philosophers of religion still debate it with the same premises.
Ibn Rushd (Averroes, 1126–1198) was a judge in Córdoba and Seville, a physician, and the author of commentaries on Aristotle so thorough that Latin scholars called him simply "the Commentator". He answered al-Ghazālī twice. In the Decisive Treatise (Faṣl al-maqāl, c. 1179–80) he asked whether philosophy is permitted by Islamic law. His argument:
Premises 4 and 5 are the contested ones, and Ibn Rushd's "elitism" is a fair criticism, as is the question of who decides when a text is to be read allegorically. He is often said to have taught a "double truth", one for philosophers and one for the people. He did not: the doctrine was attributed to thirteenth-century Latin "Averroists" at the University of Paris and condemned in 1277. His claim was that there is one truth with more than one way of reaching it.
In the Incoherence of the Incoherence (Tahāfut al-Tahāfut, c. 1180) he replied on causation: to deny that fire has a nature that causes burning is to deny that anything can be known through its causes, which is what knowing means in science. God remains the ultimate cause, acting through created causes. It is one of the great exchanges in the history of philosophy, and it was not won decisively by either side. The picture of Ibn Rushd as the end of Islamic philosophy and the start of European rationalism is a simplification: his Latin influence was large, but the tradition continued in Persian-speaking lands, in Iran and India, for centuries.
Ibn Khaldun (1332–1406), born in Tunis, served rulers across North Africa and Spain, and wrote his Muqaddimah ("Introduction") in 1377 in an Algerian fortress, in about five months by his own account. Its aim was a new science, 'ilm al-'umrān, the science of civilisation: to explain history by causes, not by anecdote. Its central concept is 'aṣabiyya, group solidarity (cohesion, "team spirit"). Tribes at the edge of a settled state have it strongly, because they depend on one another for survival; this lets them conquer a rich but divided state. Their children grow up in comfort, taxes rise, solidarity fades, and a new, tougher group arrives. He reckons the cycle at about three generations, roughly 120 years.
A toy model of one idea in the Muqaddimah. The numbers are invented for illustration; they are not Ibn Khaldun's, and real dynasties lasted from a few years to centuries. A generation is taken as 40 years, following him.
Without JavaScript: with founders at 100, a generation keeping 65% and a challenger at 30, solidarity runs 100, 65, 42, 27: the dynasty falls to the challenger in the fourth generation, after about 120 years.
Critics note that his model fits the Maghrib best, that "tribe versus city" is a simplification, and that it is not obvious how solidarity is measured. Admirers point to how early it asks for causes in climate, economy and group structure. Sociologists (see Classical Social Theory, 35/75) treat him as a founder of the field.
In Safavid Iran, Mulla Sadra (c. 1572–1640), working in Shiraz and Isfahan, reworked Avicenna. Where Avicenna held that essence and existence are two aspects of a thing, Mulla Sadra argued that existence is the fundamental reality (aṣālat al-wujūd) and essence a mental abstraction from it; existence comes in degrees of intensity, like light. His most original thesis is substantial motion (ḥaraka jawhariyya): not only the accidents of a thing (its colour, place) change, but its substance is in constant becoming. A thing is a process, not an object with changes added on. He applied it to the soul, which begins bodily and is perfected by development. His major work is the Four Journeys (al-Asfār al-arba'a). The tradition of reading it is alive today in Iran's seminaries and philosophy departments.
In the late 1660s, in the Ethiopian highlands, Zera Yacob (born around 1600 near Aksum) wrote the Hatata ("Inquiry"). According to the text he had fled persecution during the Jesuit-backed attempt to convert Ethiopia to Catholicism, hid for a couple of years in a cave, and reasoned from scratch. His arguments are plain: the world has a creator whose existence is shown by order and causation; the different religions (Orthodox, Catholic, Muslim, Jewish) each claim revelation but contradict one another, so human reason must be the test; whatever contradicts creation's evident purposes, such as slavery and the claim that celibacy is holier than marriage, cannot come from God. Whether Zera Yacob wrote it is itself an argument: in 1920 the Italian scholar Carlo Conti Rossini suggested that the Italian missionary Giusto da Urbino forged it, and Claude Sumner answered in 1976 with arguments from the text's language and ideas. Most present-day scholars accept the text as Zera Yacob's, though a minority are not persuaded. If it is authentic, it is a seventeenth-century African argument against religious coercion and for human equality, written about two decades before Locke's Letter Concerning Toleration (1689).
Ubuntu is a family of ideas, from the Nguni proverb umuntu ngumuntu ngabantu, "a person is a person through other persons". John Mbiti's 1969 formulation, "I am because we are, and since we are, therefore I am", became widely quoted. Ifeanyi Menkiti argued (1984) that personhood is achieved: you become a full person through your relations and duties, not at birth. Kwame Gyekye replied with a "moderate communitarianism", giving rights to individuals alongside duties to community. Thaddeus Metz has tried to state ubuntu as a moral theory: roughly, an action is right insofar as it honours relationships of identity and solidarity. In South Africa, judges cited ubuntu in S v Makwanyane (1995), when the Constitutional Court struck down the death penalty. The critics' question is the standard one: does a theory that grounds persons in community leave enough room to dissent from it?
Kwasi Wiredu (1931–2022), a Ghanaian philosopher, argued for "conceptual decolonization": examining which of the concepts in African philosophy come from colonial languages and which from the speakers' own, and keeping what survives argument. He also proposed that the Akan tradition of deciding by consensus is a model for democracy without party competition. And he argued that some puzzles in European metaphysics, about "being", reflect the grammar of Greek and English; Gyekye and others dispute this.
Behind these lies a dispute about what African philosophy is. In Bantu Philosophy (1945) the Belgian missionary Placide Tempels set out what he took to be a shared Bantu worldview centred on "vital force". Paulin Hountondji, from Benin, answered in the 1970s that this "ethnophilosophy" treated Africans as a single collective mind. Philosophy, he said, is argument by individuals who can be wrong, and one written down for criticism. Henry Odera Oruka (Kenya, 1944–1995) proposed an in-between: in the 1970s he interviewed Kenyan villagers with reputations as thinkers, and found some who reasoned critically, sometimes against the community's own views. He called this sage philosophy, and argued it showed that oral cultures have individual philosophers.
Match each claim to a thinker, then see what the others would add.
Without JavaScript: Tempels described a shared Bantu philosophy of vital force; Hountondji objected that philosophy needs individual argument; Oruka interviewed Kenyan sages and found critical thinkers; Wiredu worked on clearing colonial confusions from concepts and defended consensus politics.
Philosophy in Latin America begins with a political question. In 1550–51 Charles V had a committee of theologians and jurists meet at Valladolid to hear Bartolomé de las Casas against Juan Ginés de Sepúlveda. The issue was the justice of the Spanish conquest, and the argument turned on Aristotle, who had said that some people are "natural slaves", lacking the faculty of deliberation. Sepúlveda applied that to the peoples of the Americas. Las Casas, who had been a landowner in the Caribbean before becoming a Dominican, answered that they had cities, laws and arts and could be persuaded, not compelled. The judges issued no clear verdict, and the conquests went on. Las Casas also earlier had proposed bringing Africans to work in the colonies, and later repudiated this, a fact that complicates the usual picture of him.
Reconstructed from the two men's published arguments and standard accounts of the debate.
Without JavaScript: Sepúlveda says some people are natural slaves (Aristotle), so subduing them is just; Las Casas says the Aristotelian category fits few if any, that the Americas' peoples have cities, laws and religion, and that only persuasion is legitimate.
Sor Juana Inés de la Cruz (1648 or 1651–1695), a self-taught nun in New Spain, wrote a long philosophical poem on the mind's striving to know the world at a glance (Primero sueño, published 1692). Her Response to Sister Filotea (1691) answered a bishop who told her to stop secular study. Her argument is that every kind of knowledge serves understanding of the sacred, that women have the same intellects, that the church's own saints and women scholars show it, and that studying is not a defiance. In 1693–94 she gave up her library and writing; why is debated.
In the twentieth century the question became: is there a Latin American philosophy? José Vasconcelos (1882–1959), in La raza cósmica (1925), argued that the mixing of peoples in the Americas would produce a "cosmic race". The book is a landmark in how Latin America saw itself, and also, in its hierarchy of peoples, a source of criticism from Indigenous and Afro-descendant writers. In 1940 he edited a magazine sympathetic to the Axis, which harmed his reputation. In 1968 the Peruvian Augusto Salazar Bondy wrote that Latin American philosophy had been imitative because it reflected underdevelopment and dependence, and could only become authentic by overcoming them. Leopoldo Zea (Mexico, 1912–2004) replied in 1969 that Latin American philosophy should be "philosophy without more": philosophy does not need to be unique to be real, and gains authenticity by taking its own circumstances seriously.
Enrique Dussel (1934–2023), born in Argentina and later based in Mexico, developed the philosophy of liberation (Filosofía de la liberación, 1977). Its starting point is the person excluded by the existing order: the poor, the colonised, women, the indigenous. Drawing on Emmanuel Levinas's ethics of the Other, Dussel argues that a philosophy built in the centres of power takes the "totality" (the system) as given, and that the first ethical fact is the face of the person it leaves out. It sits alongside Paulo Freire's Pedagogy of the Oppressed (1968 in Portuguese, English 1970), the liberation theology of Gustavo Gutiérrez (1971) and Aníbal Quijano's notion of "coloniality of power". Critics ask whether "the Other" is a precise enough category to build a normative theory on, and whether the approach can be tested.
Three traditions carried on the central arguments of philosophy under their own conditions. Ibn Sīnā asked what is left of the self without the body and what makes existence necessary. Al-Ghazālī asked what we actually observe when we say one thing causes another, and Ibn Rushd answered that knowing means knowing causes. Ibn Khaldun and Mulla Sadra treated history and substance as processes. In Africa the question became who counts as a philosopher and what persons owe each other, and in Latin America whether the conquered are fully human and whether philosophy can be both local and real.
Try this: take any statement of the form "X causes Y" you heard today. Write down what you actually saw, and then what you added. Is the added part a law, a habit of the mind, or a guess?
Sources. Avicenna, The Healing (floating man; Necessary Existent); al-Ghazālī, Incoherence of the Philosophers, discussion 17, trans. Marmura (1997/2000); Ibn Rushd, Decisive Treatise, trans. Hourani (1961) or Butterworth (2001), and Incoherence of the Incoherence, trans. Van den Bergh (1954); the 1277 Paris condemnation; Ibn Khaldun, Muqaddimah, trans. Rosenthal (1958); Mulla Sadra, al-Asfār al-arba'a. Zera Yacob and Walda Heywat, The Hatata, ed. Sumner (1976), and Conti Rossini (1920). Mbiti, African Religions and Philosophy (1969); Menkiti (1984); Gyekye, Tradition and Modernity (1997); Wiredu, Cultural Universals and Particulars (1996); Tempels, La philosophie bantoue (1945); Hountondji, African Philosophy: Myth and Reality; Oruka, Sage Philosophy (1990); S v Makwanyane (1995). Las Casas and Sepúlveda at Valladolid, 1550–51; Sor Juana, Respuesta a Sor Filotea (1691); Vasconcelos (1925); Salazar Bondy (1968); Zea (1969); Dussel (1977). Dates of early figures are approximate.