The context for the use of this quotation was my musings on whether there is such a thing as Islamic philosophy and even Shi'i philosophy. So I came across this quotation from Heidegger's classic An Introduction to Metaphysics:
A ‘Christian philosophy’ is a round square and a misunderstanding. There is, to be sure, a thinking and questioning elaboration of the world of Christian experience, i.e, of faith. That is theology. Only epochs which no longer fully believe in the true greatness of the task of theology arrive at the disastrous notion that philosophy can help provide a refurbished theology if not a substitute fort theology, which will satisfy the needs of the time. For the original Christian faith philosophy is foolishness. To philosophise is to ask ‘why are there beings rather than nothing?’ Really to ask the question signifies: a daring attempt to fathom this unfathomable question by disclosing what it summons us to ask, to push our questioning to the very end. Where such an attempt occurs there is philosophy.