While what Derrida was on about is subject to ENDLESS debate, my view of Derrida's contribution is summed up pretty well from the wiki:
- A desire to contribute to the re-evaluation of all western values, built on the 18th century Kantian critique of reason, and carried forward to the 19th century, in its more radical implications, by Kierkegaard and Nietzsche.
- An assertion that texts outlive their authors, and become part of a
set of cultural habits equal to, if not surpassing, the importance of
authorial intent. (italics added)
- A re-valuation of certain classic western dialectics: poetry vs. philosophy, reason vs. revelation, structure vs. creativity, episteme vs. techne, etc.
This idea, that texts outlive their authors, and exceed their authorial intent, seems like a jugular issue for ex-witnesses, and those who have left or are still influenced by Christianity, Judaism, and Islam.