- Bentham (1748-1832 )
- Bradley (1846-1924)
- Comte (1798-1857 )
- Dodgson [Lewis Carroll] (1832-98 )
- Emerson (1803-82 )
- Frege (1848-1925 )
- Hegel (1770-1831 )
- Schelling (1775-1854)
- James William (1842-1910)
- Søren Kierkegaard (1813-55)
- Ernst Mach (1838-1916)
- McTaggart (1866-1925)
- Karl Marx (1818-1883)
- Martineau (1802-1876)
- Meinong (1853-1920)
- H.T. Mill (1807-1858 )
- John Stuart Mill (1806-1873)
- Nietzsche (1844-1900)
- Peir (1839-1914)
- Arthur Schopenhauer (1788-1860)
- Ludwig Feuerbach (1804 – 1872)
- Henry Sidgwick (1838-1900)
- Welby-Gregory (1837-1912)