Under the title "Grammatology," Jacques Derrida develops a theory of writing, signs, and signification that questions a number of traditional concepts and ideas, including reason, origin, subject, and history (which has always been merely a history of "reason"). In the first part of the book - "Writing Before the Letter" - Derrida outlines a theoretical foundation, which he tests in the second part - "Nature, Culture, Writing" - against a key text of European logocentrism, Rousseau's "Essai sur l'origine des langues," the reading of which becomes an exploration of the era of Rousseau. Derrida traces the functioning and issues (the historical costs) of the logocentric terminology of Western thought from Plato through Rousseau, Hegel, Husserl, Saussure, to Lévi-Strauss.