"Visionary orthodoxy" is a term Marilynne Robinson uses to describe the theology of Dietrich Bonhoeffer in her essay about him in her The Death of Adam: Essays on Modern Thought. It's a lovely phrase that captures the imaginative dimension of classical Christian theology. As she continues in the essay, Robinson goes on to give something of a definition (although that word is too technical) of what she specifies as 'great theology'. Clearly what she writes here is shaped by her engagement with Bonhoeffer, but this seems to be a more personal understanding of theology. It invites extended reflection and meditation. And it requires no commentary other than to say if this is what 'great theology' is, it is indeed a 'visionary' task that warrants our attention and energy.
Great theology is always a kind of giant and intricate poetry, like epic or saga. It is written for those who know the tale already, the urgent messages and the dying words, and who attend to its retelling with a special alertness, because the story has a claim on them and they on it. Theology is also close to the spoken voice. It evokes sermon, sacrament, and liturgy, and, of course Scripture itself, with all its echoes of song and legend and prayer. It earns its authority by winning assent and recognition, in the manner of poetry but with the difference that the assent seems to be to ultimate truth, however oblique or fragmentary the suggestion of it. Theology is written for the small community of those who would think of reading it. So it need not define freighted words like 'faith' or 'grace' but may instead reveal what they contain. To the degree that it does them any justice, its community of readers will say yes, enjoying the insight as their own and affirming it in that way.
Marilynne Robinson, "Dietrich Bonhoeffer" in The Death of Adam: Essays on Modern Thought (New York: Picador, 2005). The reference to 'visionary orthodoxy' is on p. 115 and the description of 'great theology' is on p. 117.