If you are a pagan and you follow a Greek or Roman tradition, you have the luxury of being able to read accounts of your predecessors writing about the gods as they experienced them. Homer, Virgil and other writings give an insider view of polythesitic people interacting with the gods on a daily basis, showing the way they were part of their lives. True, such writing can only have come from an elite, and what we are presented with is an idealised view, so we still can't say what it was like for ordinary people and how they regarded the gods. But things are much worse for those following other traditions such as those stemming from Britain and northern Europe. True, the Germanic gods are catered for in the work of Snorri Sturlsson and the poetry he drew upon from the Edda. And we have the sagas. But all of this was written down after the establishment of christianity. For the celtic traditions we don't even have direct stories about the gods and their attributes and have to reconstruct what we can from stories in which their presence lingers on in the guise of heroes and historical figures or in even more ephemeral tales of fairies. As for the druids, as Stuart Piggot pointed out, archaeology offers us nothing tangible, and contemporary witness, such as it is, is only a little better.
But we can reconstruct. Or can we? What must also be a problem even for those seeking to revive classical religious sensibility is that habits and modes of thought also change. The critic Northrop Frye suggested that the way that people thought in the time of Homer, the Old Testament of The Bible and other early stories up to the time of the Greek philosophers, was essentially different to habits of thought from the time of Aristotle up to the Middle Ages, and that modern modes of thought are different again. Homer, he suggests, offers metaphors which do not rely on a conscious placing of 'this for that', but simply accept both 'this' and 'that' similtaneously. For Plato, by contrast, 'this' stood for 'that' and allegory becomes the main metonymic mode. The first tends to go with polytheism. The second with monotheism. Today, Frye argues, there is only 'this' and 'that' is absent, so the dominant mode is atheism.
Can we escape the habits of thought of our age? Might the revival of polytheism suggest a new phase of thought closer to the Homeric? Can Rhiannon ride again without us asking what she represents or how she does the trick of moving at differential speeds? I think this might be a more serious problem than the lack of sources in the written record.