Philosophers (and others important in the history of philosophy), listed alphabetically:
Note: This list has a minimal criterion for inclusion and the relevance to philosophy of some individuals on the list is disputed.
I
Iamblichus () Yahya ibn Adi (893–974) Ibn Arabi (1164–1240) Ibn ar-Rawandi (827–911) Ibn Bajjah (or Avempace) (died 1138) Ibn Daud (or Rabad I or Avendauth, or John of Spain) (1110–1180) Abraham ibn Ezra (1092/3–1167) Moses ibn Ezra (1070–1138) Ibn Falaquera (1223–1290) Solomon Ibn Gabirol (1021–1058) Ibn Hazm (994–1069) Ibn Kammuna (1215–1284) Ibn Khaldun (1332–1406) Ibn Masarra (883–931) Ibn Miskawayh (940–1030) Bahya ibn Paquda (1040–1110) Ibn Sabin (1217–1268) Ibn Taymiya (1263–1328) Samuel ibn Tibbon (c. 1165 – 1232) Ibn Tufail (1110–1185) Joseph ibn Tzaddik (c. 1149) Ivan Aleksandrovich Il'in (1883–1954) Evald Vassilievich Ilyenkov (1924–1979) Immanuel the Roman (c. 1270 – c. 1330) Roman Ingarden (1893–1970) William Ralph Inge (1860–1954) José Ingenieros (1877–1925) Nae Ionescu (1890–1940) Muhammad Iqbal (1877–1938) Luce Irigaray (born 1930) Terence Irwin (born 1947) Isocrates (436–338 BC) Isaac of Stella (1105–1177) Isaac Israeli (c. 850–950) Ito Jinsai (1627–1705) Vyacheslav Ivanovich Ivanov (1866–1949)
J
Jesus of Nazareth (4 BC – AD 30 or 33) Frank Jackson (born 1943) Friedrich Heinrich Jacobi (1743–1819) Franz Jakubowski (1912–1970) James of Viterbo (1255–1308) Henry James Sr. (1811–1882) William James (1842–1910) Fredric Jameson (born 1934) Vladimir Jankélévitch (1903–1985) Karl Jaspers (1883–1969) Jayarāśi Bhaṭṭa (fl. c. 800) James Hopwood Jeans (1877–1946) Thomas Jefferson (1743–1826) Richard C. Jeffrey (1926–2002) William Stanley Jevons (1835–1882) Rudolf von Jhering (1818–1892) Jinul (or Chinul) (1158–1210) Joachim of Fiore (1135–1201) Friedrich Jodl (1849–1914) John of Damascus (c. 676–749) John of Jandun (1280–1328) John of La Rochelle (1190–1245) John of Mirecourt (c. 1345) John of Paris (1260–1306) John of Salisbury (c. 1115–1180) John of St. Thomas (or Jean Poinsot) (1589–1644) John of the Cross (1542–1591) Alexander Bryan Johnson (1786–1867) Samuel Johnson (1649–1703) Samuel Johnson (1696–1772) Samuel Johnson (1709–1784) William Ernest Johnson (1858–1931) Constance Jones (1848–1922) Jørgen Jørgensen (1894–1969) Théodore Simon Jouffroy (1796–1842) Judah ben Moses of Rome (orJudah Romano) (1292–1330) Carl Jung (1875–1961) Ernst Jünger (1895–1998) Joachim Jungius (1587–1657) Justinian I (483–565) Al-Juwayni (1028–1085)
K
Franz Kafka (1883–1924) Kaibara Ekiken (1630–1740) Kang Youwei (1858–1927) Milan Kangrga (1923–2008) Immanuel Kant (1724–1804) Kao Tzu (c. 420 – 350 BC) David Kaplan (born 1933) Mordecai Kaplan (1881–1983) Nikolai Ivanovich Kareev (1850–1931) Lev Platonovich Karsavin (1882–1952) Joseph Kaspi (1279–1340) Walter Kaufmann (1921–1980) Karl Kautsky (1854–1938) Khedrup Gelek Pelzang (1385–1438) Konstantin Kavelin (1818–1885) Bartholomew Keckermann (1571–1609) Hans Kelsen (1881–1973) Norman Kemp Smith (1872–1958) Anthony Kenny (born 1931) Johannes Kepler (1571–1630) John Maynard Keynes (1883–1946) Hermann Graf Keyserling (1880–1946) Aleksey Khomyakov (1804–1860) Søren Kierkegaard (1813–1855) Richard Kilvington (1302–1361) Robert Kilwardby (1215–1279) Jaegwon Kim (1934–2019) Al-Kindi (801–873) Martin Luther King Jr. (1929–1968) Athanasius Kircher (1602–1680) Ivan Kireevsky (1806–1856) Patricia Kitcher (born 1948) Ludwig Klages (1872–1956) Heinrich von Kleist (1777–1811) William Calvert Kneale (1906–1990) Martin Knutzen (1713–1751) Ko Hung (4th century) Kurt Koffka (1886–1941) Wolfgang Köhler (1887–1967) Alexandre Kojève (1902–1968) Leszek Kołakowski (1927–2009) Alejandro Korn (1860–1936) Karl Korsch (1886–1961) Karel Kosík (1926–2003) Tadeusz Kotarbiński (1886–1981) Alexandre Koyre (1892–1964) Aleksei Aleksandrovich Kozlov (1831–1901) Karl Kraus (1874–1936) Karl Christian Friedrich Krause (1781–1832) Georg Kreisel (1923–2015) Saul Kripke (born 1940) Jiddu Krishnamurti (1895–1986) Uppaluri Gopala Krishnamurti (1918–2007) Julia Kristeva (born 1941) Nachman Krochmal (1785–1840) Leopold Kronecker (1823–1891) Peter Kropotkin (1842–1921) Felix Krueger (1874–1948) Thomas Samuel Kuhn (1922–1996) Kūkai (774–835) Kuki Shūzō (1888–1941) Oswald Külpe (1862–1915) Kumārila Bhaṭṭa (fl. roughly 700) Kumazawa Banzan (1619–1691) Kuo Hsiang (or Guoxiang) (died c. 312)