In the political supplements of newspapers and in public debates, it is often claimed that "Islam" as such is archaic and poorly developed because in contrast to Europe it has not gone through a phase of Enlightenment. But it often remains unclear what the word "Enlightenment" is being used to mean here. This volume recalls the legacy of the European Enlightenment and argues in favour of nuanced and reason-based thinking in the style of Immanuel Kant. When one follows these principles, currents of thought shaped by Islam can indeed be seen to be enlightened, as the examples of liberal Muslims today and Arabic thinkers in the past impressively show. The author argues in favour of an "expanded thinking" in the twenty-first century that would be capable of safeguarding the legacy of the Enlightenment and in encounters with Islam would show that even today the Enlightenment can still make a vital contribution to understanding others.