The concept of primary sources comes most naturally to the study of history: works created during the period or by the people that we are studying. It is also found in other areas of study such as philosophy. In philosophy primary sources include works created by philosophers: their philosophical treatises, letters, autobiographies, diaries, notebooks, interviews, etc. These provide the most direct and reliable evidence for interpreting their thought. By contrast, secondary works are written by other people: reviews, articles, and books about a particular philosopher's works. Secondary works typically interpret or react to primary works.
Examples of primary sources (cited in MLA 7 style):
Kant, Immanuel. Gesammelte Schriften. 29 vols. to date. Berlin: W. de Gruyter, 1969- . Print.
Kant, Immanuel. Notes and Fragments. Ed. Paul Guyer. Trans. Curtis Bowman, Paul Guyer, Frederick Rauscher. Cambridge: Cambridge UP, 2005. Print. The Cambridge Edition of the Works of Immanuel Kant in Translation.
Quine, W.V. The Time of My Life: An Autobiography. Cambridge: MIT P, 1985. Print.
Wittgenstein, Ludwig. Wittgenstein in Cambridge: letters and documents, 1911-1951. Ed. Brian McGuinness. 4th ed. Malden: Blackwell, 2008. Print.
Wittgenstein, Ludwig. Wittgenstein's Lectures, Cambridge, 1932-1935: from the notes of Alice Ambrose and Margaret Macdonald. Ed. Alice Ambrose. Chicago: U of Chicago P, 1982. Print.
Some Examples of Secondary Sources:
Donohoe, Janet. "The Place of Tradition: Heidegger and Benjamin on Technology and Art." Journal of the British Society for Phenomenology 39.3 (2008): 260-274. Print.
Irwin, Terrence. Plato's Ethics. New York: Oxford UP, 1995. Web. 5 Aug. 2009.
Massie, Pascal. "Between Past and Future: Aristotle and the Division of Time." Epoche 13.2 (2009): 317-329. Print.
Zuckert, Rachel. Kant on Beauty and Biology: An Interpretation of the Critique of Judgment. Cambridge: Cambridge UP, 2007. Print.
The above examples illustrate some of the variety of primary and secondary sources. It can become more complicated. If we are studying the history of philosophy, works by other people from the same era, such as contemporary reviews and responses, may also be considered primary sources for understanding the reception of a particular philosopher or school of thought in that era. So the same type of work may be considered a primary or secondary source, depending on approach and perspective.
