Karl Rahner

God, as transcendental experience, is a 'horizon' rather than a 'thing':

"The horizon cannot be comprised within the horizon ... the ultimate measure cannot be measured; the boundary which delimits all things cannot itself be bounded by a still more distant limit" [Rahner, Theological Investigations, IV:51]

(Rahner's favourite image, the image to which he returns most frequently, is that of a horizon', Karen Kilby, Karl Rahner (SPCK 2007), 5) Only a metaphor, of course; but arguing by metaphors is dangerous. Because the horizon is virtual not actual, nothing more than a product of the particular location of our perception. There is no 'horizon' as such on the Earth. Or to put it another way: as atheists are fond of saying of God, it doesn't exist, it only seems to exist on account of where we happen to be standing.' That's not where Rahner hopes to go with this image, of course.

We are perfectly entitled to think of the creation and of the incarnation, not as two disparate, adjacent acts of God ... but as two moments and phases in the real world of the unique, even though internally differentiated, processes of God's self-renunciation and self-expression into what is other than himself. [Theological Investigations, V:177-8]

This reads rather as wish-fulfillment, a desire to smooth over the gnarliness of the actual narrative -- the (whisper it) whiff of arbitrariness of creating the cosmos and then, after billions of years, adding a second divine incarnation to it.

There can be people who consider themselves atheists whilst in truth they affirm God, for example, by unconditional dedication to an honest search for truth, or by fidelity to the absolute judgement of conscience. [On Heresy, 16]

This, on the other hand, seems to shy away from one of the things that is distinctive about Rahner's thought: the sense of the divine as a radical alterity. Here the desire to bring atheists into the communion of Rahner's church, whether they like it or not, looks like a shying away from that organising principle.