Very recently a parishioner asked** me about the Church's view on mediums. Apparently there is a popular television show that features a medium. (I suppose popularity makes for a happy medium.) (I further suppose that I should get to the response.)
Paragraph 2116 of the Catechism of the Catholic Church states:
All forms of divination are to be rejected: recourse to Satan or demons, conjuring up the dead or other practices falsely supposed to "unveil" the future (Dt 18:10; Jer 29:8). Consulting horoscopes, astrology, palm reading, interpretation of omens and lots, the phenomena of clairvoyance, and recourse to mediums all conceal a desire for power over time, history, and, in the last analysis, other human beings, as well as a wish to conciliate hidden powers. They contradict the honor, respect, and loving fear that we owe to God alone.
Since the earliest days people have tried to gain greater certainty over the unknown by occult practices. Remember how Saul's attempt to invoke Samuel blew up in the former's face (1 Sam 28:4-19). Many people are not content to trust in the merciful and wise plan of God. In the face of personal tragedy, loss of work, bereavement, etc., the "desire for power" begins to manifest. The CCC astutely notes that the real object of this power is "other human beings," because time and history...well, they're too abstract and sublime, but this troublesome situation or inscrutable individual is a bit easier to grasp.
Are occult practitioners insincere? What are they actually doing when they claim to exercise such powers? Does Satan enter such people in order to equip them for his "ministry"? I can't answer for occult practitioners or Satan; but the latter, as crafty as he is, tries whatever he can to distract souls from living the truth in love.
Can't God communicate His will through people?--Yes, the NAB footnotes say, but that happens precisely by His choice and not by the manipulation of a human being. Angels fulfill that very function as divinely appointed messengers, not as fabrications of our wishful thinking.
More to the point of the Catechism paragraph is the "honor, respect, and loving fear" due only to God. This is the positive value affirmed in the prohibition of divination. God described Himself as "jealous" (Dt 4:24 et al) not in the sense that our straying diminishes His sense of worth, or damages His Self-perception, but rather that He wants all of us, without reservations born of distrust. He wants us for our sake, so that we may achieve the fullness of life that He wills for us. Easily distracted as we are, we don't seem to want that fullness of life for us as much as He does; or we want it, but sabotage our pursuit of it by our weak desire, clouded understanding, or unbridled emotions. Contrary to what we may think, the fear of God is a liberating fear and not a paralyzing one. It frees us for the pursuit of heaven by placing our concerns, daily or overarching, in the larger context of His best interests for all humanity.
Now it may be that some people are able to view horoscopes and watch fortune-tellervision "for entertainment purposes only." Jesus told the apostles that they could pick up serpents (cf. Mk 16:18). According to the text of Alcoholics Anonymous, sober alcoholics well immersed in the program could possibly enter places which serve alcohol. Apostles and addicts must, however, be acutely aware of their motives and be spiritually fit, lest they get bitten or blotto. Some demons can be expelled only "by prayer" (Mk 9:29; variant readings include "and fasting"). Growing up I always heard the wise counsel not to mess with the devil. I certainly strive to improve my spiritual fitness; but the goal of such exercises is not to achieve mastery over the unknown factors in my life, but rather to grow in the strength needed to accept my limits.
Now it may be that some people are able to view horoscopes and watch fortune-tellervision "for entertainment purposes only." Jesus told the apostles that they could pick up serpents (cf. Mk 16:18). According to the text of Alcoholics Anonymous, sober alcoholics well immersed in the program could possibly enter places which serve alcohol. Apostles and addicts must, however, be acutely aware of their motives and be spiritually fit, lest they get bitten or blotto. Some demons can be expelled only "by prayer" (Mk 9:29; variant readings include "and fasting"). Growing up I always heard the wise counsel not to mess with the devil. I certainly strive to improve my spiritual fitness; but the goal of such exercises is not to achieve mastery over the unknown factors in my life, but rather to grow in the strength needed to accept my limits.
For the reader's edification, consult this link on the subject from Catholic Culture.
**I very much enjoy the effort to research and articulate the Church's teachings. So ask away!