Grayling impugns this stance by saying that such ‘evidence’ could never come to pass, nothing would ever serve to prove the existence of God. In effect evidence that could never become manifest is not evidence at all. The agnostic then is a confused atheist that wants a firm talking to. It's the old 'tooth fairy' argument.
This position of Grayling’s is a 'buck up man, stop being windy' retort to a Dawkins stance. It is to be contrasted to the apophatic mystical. God in whom we live, move and have our being is not an object of empirical observation, we will not stumble on it while looking for the tv remote.
The agnostic stance may be a valid position emotionally but faulty from a purely intellectual point of view. People like to keep their options open. This is why paint shops sell testers. However thinking it through, looking for definitive evidence is to have failed to appreciate what the entity in question is. Something that can be settled empirically even though there is a remote possibility of that eventuality ever coming to pass is not adequate to any serious concept of God. That we do not know is true but that we cannot know is also true. We cannot know because the intellectual equipment is not adequate to that purported object. If God is not an object he/she/it cannot be known. Therefore without some sort of realisation of God however limited that might be, the atheistic position is to this believer the intellectually respectable one. Is Grayling that sort of atheist? He has taken a stance about supernatural agencies and their incredibility on the basis that there is no evidence that could not reasonably be forthcoming. Colour me atheist.
Who then is an atheist in the heroic sense that I have been urging? A contender might be the philosopher Simon Critchley whose influences are continental and therefore large positions are second nature to him. Interviewed on http://www.culturewars.org.uk/2002-12/simoncritchley.htm re his book on humour he has this to say:
Are you suggesting that in a secular age, humour is the new God?
SC: This is an important question and it strikes me that there are about twenty things to say. First, there is no God. I begin from the assumption that modernity is defined by the impossibility of any metaphysical belief in a deity. That's where I begin from and that is axiomatic for me. It means that if I had a religious experience I would stop doing philosophy: philosophy for me is essentially atheistic.
Now that's an anxious atheism. It's an atheism that is anxious because it inhabits questions that were resolved religiously in the pre-modern period. So the difficulty of modern life, of modernity in the full sense is this: the way in which we make sense of ourselves, those things we value and attribute meaning to, is still within a religious framework. Yet we cannot believe that religious framework. So from my perspective, modernity as a fully secular worldview has never really been achieved. We still inhabit the traces, the memory of, that religious perspective. And that's an ambiguous thing.
Critchley being English has an acute sense of the folly of portentousness so I suppose it is a mark of his commitment that he ventures so far into an irony free zone. I respect that. His position on deity is a metaphysical transcendental one. Empirical confirmation or disconformation is senseless.There is no 'waiting for Godot'.