In his introduction to his novel "Tarot", Piers Anthony talks about an experimental Tarot reading he did as part of his research for the novel, a reading that went very well, too well in his opinion. Being a non-believer, he asks “How could a supernatural device work so well for an unbeliever?” His answer, after much thought was: “[T]he tarot deck presents a concentration of symbols, some of which are almost certain to relate to any person. The pictures have multiple levels, many interpretations, and these are what the person tunes in on. If Death comes up and there has been a recent death in the family, there is confirmation. If there has not been a death, then there is the fear of one coming up. If there is no such fear, the symbol may relate to the termination of something important, such as one’s job. Death is not just literal death; it is Transformation, or Change, and can manifest in many ways. Similarly, the other symbols have projections like pincushions; you can’t touch them without getting stuck. The Lovers is also Choice, so that card relates to romance or to a difficult decision; and when was there a time when you are not faced with some decision, and which one is ever simple? Os these versatile symbols, coupled with the human’s mind capacity to interpret, to make something relate, do almost inevitably relate to your life.” As he concludes, he had “solved the mystery."
As an initiate of Golden Dawn, I don’t necessary agree with his answer, but I must admit that his opinion is one of the better non-initiated, non-believer answers that I have encountered about how the Tarot works.