The nineteenth-century German theologian Rudolf Otto, in his book The Idea of the Holy, popularized the term "numinous", an adjective describing the sense of mystery and wonder that purportedly stems from the presence of a deity. According to Otto, the sense of the numinous had two main characteristics: the mysterium tremendum, the sense of fear and trembling that comes from the presence of that which is wholly other, and the mysterium fascinas, the sense of fascination and curiosity that such an experience evokes.

Otto's theology concisely sums up the categories of religious experience. But the problem with his conception of the numinous is that it lacks one very important quality - understanding.