What material would you consider absolutely essential from the literary and philosophical fields to supplement a study of European history after roughly 1648 (for high school seniors and university undergraduates)? Why?
If you are pursuing this in pure philosophical terms, I think reading the Descartes, Kant, Hegel, Marx, Nietszche sequence is critical. In being able to trace the growth of political liberalism and its countervailing force which emerges into modernism and post modernism is extremely important. This would also allow you to engage in a study of Heidegger, Sartre, and Foucault as well as Derrida. This is heavy on the philosophical level, but being able to articulate the progression of modernism to realism to post modernism can prove to be liberating to students being exposed to intellectual history. I think that in terms of science, Darwin, as the previous post suggested, is essential. Reading Freud's Civilization and Its Discontents, would also be extremely powerful to analyze from a philosophical point of view. In terms of literature post 1648, you could do a study of how modern tragedy is the appropriation of the world in accordance to one's subjectivity. This will give you the perfect literary counter punch to the philosophy. Shelley's Frankenstein, Goethe's Faust, Flaubert's Madame Bovary, as well as Dostoyevsky's Notes from the Underground can examplify this theme in a lucid fashion.
I teach in a classical school. Our modern history students read at least excerpts from John Locke, Two Treatises of Government, and Edmund Burke, Reflections on the French Revolution. We choose these two texts because we feel that we can use them to show the connection between the realm on intellectual history and the actual practise of politics. These works help us understand the development of the American political system and the differences between both ideal and practice in the American and French Revolutions. We will also be reading Marx and Darwin because of the effect their ideas have had on modern thought and life. In the companion literature class, the students will read Dickens, A Tale of Two Cities, Bronte, Jane Eyre, and Koestler, Darkness at Noon, which explore issues of of intellectual, religious, and political culture of their times. I am still working on developing this course which is for High School Juniors and Seniors.