Barth's approach tears up any possibility of dialogue between faith and unfaith or between theology and other human sciences. Theology just says what it says on the basis of scripture, and that's that.

Ultimately, we live in the face of an irresolvable mystery about our origin and, for that matter, about our end. And what Schleiermacher would have us do is (a) acknowledge that this is the case and (b) accept it as something positive, a point of departure for a life of trusting joy.

Religious life is about something real in human experience that is not constrained by what Wittgenstein called 'all that is the case'. In this sense Heidegger is not simply 'mistaken' - he just asks us, as philosophers mostly do, to think more carefully about what we're saying.

And this is also what he takes Christian doctrine, in all its complexity, to be centrally about, that is, teaching an attitude rather than a set of propositions. Call it joyous openness to life. What's not relevant about that?

In a sense these are questions that most people ask themselves to some extent. They become philosophical when asked with a persistence and rigour that pushes past conventional or evasive answers. It's nothing to do with acquiring a technical facility in an academic discipline.

Schleiermacher, however, starts by attempting to find what he takes to be a basic element of the human condition as such, namely, that we did not invent ourselves but find ourselves born into a life and a world that precedes us in manifold ways.

Ethics arises in the recognition of our obligation to care for others as beings, like us, exposed to mortality - that is, beings who need our help. Buddhism, not wrongly, extends this to 'all sentient beings'.