In the background of some of the more salient discussions of late to do with religion, and popularized by CS Lewis in particular, is the concept of the numinous. Here is the relevant passage, according to wikipedia:
C.S. Lewis described the numinous experience as follows in The Problem of Pain:
Suppose you were told there was a tiger in the next room: you would know that you were in danger and would probably feel fear. But if you were told "There is a ghost in the next room," and believed it, you would feel, indeed, what is often called fear, but of a different kind. It would not be based on the knowledge of danger, for no one is primarily afraid of what a ghost may do to him, but of the mere fact that it is a ghost. It is "uncanny" rather than dangerous, and the special kind of fear it excites may be called Dread. With the Uncanny one has reached the fringes of the Numinous. Now suppose that you were told simply "There is a mighty spirit in the room," and believed it. Your feelings would then be even less like the mere fear of danger: but the disturbance would be profound. You would feel wonder and a certain shrinking—a sense of inadequacy to cope with such a visitant and of prostration before it—an emotion which might be expressed in Shakespeare's words "Under it my genius is rebuked." This feeling may be described as awe, and the object which excites it as the Numinous.[8]
As the term owes its derivation ultimately to Rudolf Otto, you might as well look up the primary text, which is freely available: The Idea of the Holy. It's one of those books you need not read all the way through, or even very much of, in order to get the gist; but if you do, it's something you can then just as easily spend an hour or a week just thinking about a sentence or a paragraph from, as reading all the words of. One interesting thing to note is that Otto cautions us right up front against facile appropriation of his work of just the sort which it is so often put to, and which I am sure I am just as prone to as anyone:
... I feel that no one ought to concern himself with the Numen ineffablile who has not already devoted assiduous and serious study to the Ratio aeterna. (Foreword)
Time to brush off my Euclid and Aquinas, I guess. I came to Otto not via Lewis, most of whose apologetic work I'm still unfamiliar with, but from reading Karen Armstrong, on Pullman's recommendation. And even with that, it might not have made it to the top of my reading list if not for the curious prominence, not of the numinous as such, but of the word Holy, in the Final Fantasy series. But more on that another time.
Anyhow, Otto's Idea of the Holy proved to be such a powerful corrective to the rational studies dominant before his time, outside Nietzsche and Freud, and hanging on today in all sorts of reactionary positivism and New Atheism, that now we can speak perfectly comfortably of the spiritual or the numinous or the holy, until we stop to think for a moment about what it is we mean by them. Still, that's been true since Socrates, as Kierkegaard so exhaustively pointed out, or as Lewis, memorably, puts it in the mouth of one of his characters: "it's all in Plato!"
To highlight just a couple of more recondite connections worth attention, though: Auerbach, in his masterpiece Mimesis, has a discussion of creatureliness, a topic which may also have been popularized by Otto but which you don't hear much about anymore. Effectively, it's the opposite of the Holy, that in us by which, paradoxically, we recognize the Holy as wholly Other. Another expression of the core idea gets developed in terms of music, where Otto refers us to the well-documented holy genius of Bach (Credo, Mass in B Minor), as well as a couple of less conspicuous exemplars: Mendelssohn (Psalm 2) and Thomas Luiz / Tomas Luis de Victoria (Popule meus).
continued: see Devotional Language, by Johannes Sloek