The Bible contains strong warnings against anything connected with spiritism. For example, it states:
“There should not be found in you . . . anyone who employs divination, anyone practicing magic, anyone who looks for omens, a sorcerer, anyone binding others with a spell, anyone who consults a spirit medium or a fortune-teller, or anyone who inquires of the dead. For whoever does these things is detestable to Jehovah.”—Deuteronomy 18:10-12.
Spiritism promotes alliance with demons. The Bible teaches that some angels rebelled against God and made themselves his enemies. (Genesis 6:2; Jude 6) These wicked angels, called demons, mislead people through spirit mediums, fortune-tellers, and those who practice divination and astrology. Practicing these things would align us with enemies of God.
Spiritism promotes the false belief that certain humans can predict the future. However, only God can say: “From the beginning I foretell the outcome, and from long ago the things that have not yet been done.”—Isaiah 46:10; James 4:13, 14.
Spiritism promotes the false belief that the dead can communicate with the living. However, the Bible says: “The dead know nothing at all . . . There is no work nor planning nor knowledge nor wisdom in the Grave.”—Ecclesiastes 9:5, 10.
https://www.jw.org/en/bible-teachings/teenagers/ask/is-occult-harmless/
