The phenomenological character of mystical experience is not that hard to understand, at least in principle, and as a matter of abstract theory. Withdraw attention from all particular things and their qualia – including oneself – as all mystical disciplines insist their students should do, and in the limit the only quale remaining will be that of sheer being. But to experience sheer being is to experience something of what being is like for God, who is Being as such. Being is the basic good, the good of which all other goods are portions; so the feeling of being as such is blissful.
Being as such is not nothing, NB. On the contrary, it is the only category that comprehends everything. Thus mystical experience does not necessarily involve paucity of apprehension, a dwindling or diminution of the richness of experience, or its detail, or its breadth, or depth. It is not less than quotidian experience, but far more – not just sublime and panoptic, but superlime, synoptic, spacious, and scient to the degree that it is pure and simple. As the experience of the most basic truth, moreover, it is the experience of God, who is Truth: to feel the utmost basis of one’s own being is to feel God, of and in and by whom all things exist.
In practice, of course, it is quite difficult to understand mystical experience; to try to understand it in practice is rather to miss the point of the mystical project, and thus to frustrate it; for one of the things the mystic must set aside is the effort to understand. It is hard furthermore to forget particular things, and once having done so, and achieved simplicity, it is then impossible to parse it in particular terms – the only sort available to us.