Ross: This is what I think is so impressive about the Spanish accounts, which are careful to say a spell or incantation beforehand - there is a direct appeal to the hidden world of the spirits. This kind of thing is explicit even in the Golden Dawn's long method - "serious" occultists taking divination as seriously as the "superstitious" witchcraft methods.
But such methods, and even the belief system of modern sophisticated card-readers has neither appeal to the spirits nor belief in the superior insight of the reader - it is something completely different nowadays,
In earlier times it seems that card-readers and such needed to voice (or otherwise display) their intentions, a declared acknowledgment of whatever deities or belief system was appropiate to those time(s) & place(s). In some systems it is still considered important to manifest (openly state on the Earth Plane) your undertakings. But that's usually in ritual Lodges/Circles
Even today many readers (and querents) still do a silent prayer (or whatever) at the start of any divination. But most people are aware that it's the Intention - to do no harm, or to help objectively, or to be of benifit - that is the principal thing. And this might be described as an attitude or inner conviction. A focussed mind-set which may or may not include a spiritual belief. It is therefore 'silent', not spoken aloud.