John Stuart Mill, On Liberty (1859)
Charles Darwin, On the Origin of Species (1859) [Note: On the Origin of Species is not a philosophical text per se, but is nevertheless listed here for its enormous influence on philosophical thought.]
Kostis Palamas (January 13)
Edmund Husserl (April 8)
Henri Bergson (October 18)
John Dewey (October 20)
Alexis de Tocqueville (April 16)
Alexander von Humboldt (May 6)
1859 in philosophy Wikipedia (Text) CC BY-SA