Ontologists

Aristotle (; 384–322 BC) was an ancient Greek philosopher and polymath. His writings cover a broad range of subjects spanning the natural sciences, philosophy, linguistics, economics, politics, psychology, and the arts. As the founder of the Peripatetic school of philosophy in the Lyceum in Athens, he began the wider Aristotelian tradition that followed, which set the groundwork for the development of modern science.

German-born philosopher (1818-1883)

Russian author (1828–1910)

François-Marie Arouet (; 21 November 169430 May 1778), known by his pen name Voltaire (, ; ), was a French Enlightenment writer, philosopher (philosophe), satirist, and historian. Famous for his wit and his criticism of Christianity (especially of the Catholic Church) and of slavery, Voltaire was an advocate of freedom of speech, freedom of religion, and separation of church and state.

German philosopher (1724-1804)

French philosopher, mathematician, and scientist (1596–1650)

French existentialist philosopher (1905–1980)

Ibn Sina ( – 22 June 1037), commonly known in the West as Avicenna ( ), was a preeminent philosopher and physician of the Muslim world. He was a seminal figure of the Islamic Golden Age, serving in the courts of various Iranian rulers, and was influential to medieval European medical and Scholastic thought.

Avram Noam Chomsky is an American intellectual, philosopher, linguist, political activist, and social critic. Sometimes called "the father of modern linguistics", Chomsky is also a major figure in analytic philosophy and one of the founders of the field of cognitive science. He is a laureate professor of linguistics at the University of Arizona and an institute professor emeritus at the Massachusetts Institute of Technology (MIT). Among the most cited living authors, Chomsky has written more than 150 books on topics such as linguistics, war, and politics. In addition to his work in linguistics, since the 1960s, Chomsky has been an influential voice on the American Left as a consistent critic of the foreign policy of the United States, contemporary capitalism, and corporatocracy.

English philosopher and statesman (1561–1626)

Dutch philosopher (1632-1677)

Austrian philosopher and logician (1889–1951)

ancient Greek philosopher and mathematician

English philosopher (1588–1679)

French Enlightenment philosopher writer and encyclopædist (1713–1784)

German philosopher (1889–1976)

Heraclitus (; ; ) was an ancient Greek pre-Socratic philosopher from the city of Ephesus, which was then part of the Persian Empire. He exerts a wide influence on Western philosophy, both ancient and modern, through the works of such authors as Plato, Aristotle, the Stoics, Georg Wilhelm Friedrich Hegel, Friedrich Nietzsche, and Martin Heidegger.

Ibn Rushd (14 April 112611 December 1198), Latinized as Averroes, was an Andalusian polymath and jurist who was proficient in a variety of intellectual fields, including philosophy, theology, medicine, astronomy, physics, psychology, mathematics, neurology, Islamic jurisprudence and law, and linguistics. The author of more than 100 books and treatises, his philosophical works include numerous commentaries on Aristotle, for which he was known in the Western world as "The Commentator" and "Father of Rationalism".

Austrian-British philosopher of science and social and política e falsificationism and for criticism of Plato, Hegel and Marx as totalitarian opponents of open society (1902-1994)

American philosopher, psychologist, and pragmatist (1842–1910)

Nāgārjuna (, ; ) was an Indian philosopher and Mahāyāna Buddhist monk of the Madhyamaka (Centrism, Middle Way) school. Nāgārjuna is widely considered one of the most important Buddhist philosophers. He was the founder of the Madhyamaka school of Buddhist philosophy and a defender of the Mahāyāna movement. His Mūlamadhyamakakārikā (Root Verses on Madhyamaka, MMK) is the most important text on the Madhyamaka philosophy of emptiness. The MMK inspired a large number of commentaries in Sanskrit, Chinese, Tibetan, Korean and Japanese and continues to be studied today.

Austrian-American logician, mathematician, and philosopher of mathematics (1906-1978)

American philosopher, psychologist, and educational reformer (1859–1952)

German philosopher and anthropologist (1804–1872)

Mencius (孟子, Mèngzǐ, ; ), born Meng Ke (), was a Chinese Confucian philosopher, often described as the Second Sage () to reflect his traditional esteem relative to Confucius himself. He was part of Confucius's fourth generation of disciples, inheriting his ideology and developing it further. Living during the Warring States period, he is said to have spent much of his life travelling around the states offering counsel to different rulers. Conversations with these rulers form the basis of the Mencius, which would later be canonised as a Confucian classic.

German philosopher, known as the father of phenomenology (*1859 – †1938)

French anthropologist and ethnologist (1908–2009)

English mathematician and philosopher (1861–1947)

French philosopher (1930–2004)

Slovenian philosopher (born 1949)

thumbnail|200px|Postage stamp of the USSR, issued on the 1100th anniversary of the birth of Al-Farabi (1975) Abu Nasr Muhammad al-Farabi (; – 14 December 950–12 January 951), known in the Latin West as Alpharabius, was an early Islamic philosopher and music theorist. He has been designated as "Father of Islamic Neoplatonism", and the "Founder of Islamic Political Philosophy".

American science fiction author (1928–1982)

8th-century Hindu philosopher and theologian- Restorer of “Dashanami Sampradaya”.

11th‑century Benedictine monk, Archbishop of Canterbury, philosopher and theologian

German philosopher, logician, and mathematician (1848–1925)

German philosopher (1806-1856)

German historian and philosopher (1880-1936)

Swedish 18th century scientist and theologian (1688-1772)

French philosopher (1925–1995)

Spanish liberal philosopher and essayist (1883–1955)

Abū Yūsuf Yaʻqūb ibn ʼIsḥāq aṣ-Ṣabbāḥ al-Kindī (; ; ; ) was an Arab polymath who was active as a philosopher, mathematician, physician, and music theorist. Al-Kindi was the first of the Islamic peripatetic philosophers, and is hailed as the "father of Arab philosophy".

French philosopher and essayist

German-born French philosopher (1723–1789)

Spanish-American philosopher

Romanian-French philosopher and essayist (1911–1995)

American philosopher, logician, mathematician, and scientist (1839-1914)

German philosopher (1900–2002)

German philosopher (1874-1928)

French philosopher, Jesuit priest, and paleontologist

English cleric and cardinal (1801–1890)

Hungarian marxist philosopher and literary critic (1885–1971)

German philosopher and logician (1891–1970)

Mozi, personal name Mo Di,

German theologian, philosopher, and biblical scholar (1768-1834)

German philosopher and sociologist (1895–1973)

American philosopher and logician (1900–2000)

Bohemian mathematician and priest (1781–1848)

French philosopher, playwright, music critic and leading Christian existentialist (1889-1973)

French philosopher