Tim Powers writes a lot of fiction about magical topics but is himself a conservatively religious sort of guy. I quite respect that sort of attitude–cautious awareness of the wider spiritual world joined to a serious respect for the very humane spiritual traditions that have traditionally been kind to people qua people. Anyway, I quite like the way he portrays Tarot in his book Last Call (which seems to mirror his own personal distrust of Tarot): when you spread out the cards, the spirit world has a chance to look at you. It is something of a one-way mirror, so that while you see in the reading yourself and your situation, the spirits see you. Like a one-way mirror, you can’t always tell if there is someone on the other side, but there might be.
I am obviously more sanguine about that process than Powers (I own and use Tarot decks, plural, after all), but my sense of the process isn’t too different from his own. Part of the issue for me is that, whether you open the window for them or not, your life runs parallel to the life of spirits. The one-way mirror analogy is especially good here. There is a partition between the world of the living and the world of spirits and that partition can be made to shine, illuminating our side but thereby making it easier for those on the other side to see us. They are already there, though, and already have a dim view of us through unlit partition; the divination just gives them a chance to get a better sense of things.
Obviously, if the spirits running alongside you in life aren’t so good, this can be a bit of a problem, but in general most of us old enough to shuffle a deck have a number of spirits around us that are basically beneficent. Giving them a chance to take a better look at what it is they are beneficently disposed to is often fine enough. You’ll want to be mindful of where and when you do the divination, probably pay attention a little to the diviner if you aren’t divining for yourself, but otherwise, rock on. In most cases, the act of divination seems to reinforce the partition, so it can even be a minor but real spiritual safety measure in the face of spiritual disorder.
This implies that there is a corollary process, in which we might glimpse the world of spirits more clearly and I wonder if some spontaneous spirit encounters are of this sort, the flashing of a spirit looking at itself in the partition, thereby giving us a better glimpse of them. Regardless, both of these processes would stand in contrast to forms of mediumship and seership in which the partition softens, allowing for the two worlds to be folded over each other.
Contrast isn’t opposition, of course, and it is possible for a diviner to make use of their mediumistic skills simultaneously with a divination. I have often found mediumistic alertness a useful complement to divination both with Tarot and with runes. On occasion, the reading itself will light up with a spiritual presence out of proportion to the divination, leaving me to wonder if on occasion the reading becomes a kind of talismanic body, a vehicle into which a spirit may extend itself into the partition.
Of note, is that this phenomenon is alien to my work with the I Ching. The I Ching seems to operate according to a different mechanism. The Tarot and the runes seem to partake of a lunar occultism, an intimacy with the boundary that separates the quick and the dead, with the traces which may be reoccupied, while the I Ching…if pressed, I would suggest that it partakes of the Albus face of Mercury. It has an intelligence and personality all its own. It possesses a gentle, insistent, and expansive interest in the good and orderly. The risks of lunar occultism are absent here.