Video from Crossexamined.org
"Why does the Bible prohibit talking to spirits if they don't exist?" Q & A
“Beloved, do not believe every spirit, but test the spirits to see whether they are from God, for many false prophets have gone out into the world” (1 John 4:1).
In this verse believers are commanded to “test the spirits to see whether they are from God.” This same command is echoed in other parts of Scripture as well. For example, in 1 Thessalonians 5:20-21 we find Paul exhorting the Christians to not “despise prophecies, but test everything; hold fast what is good.”
These two passages are just a few of the many that warn Christians to test the message that people or spirits proclaim. This is true in all situations but most importantly when a person or spirit is claiming to speak for God. Christians are to be discerning hearers and readers of all messages. The reason for the admonition to “test the spirits” or “test all things” is that there are “many false prophets” or “wolves in sheep’s clothing” that try to lead Christians astray. Sadly, there are many people who claim to speak for God who are presenting a false gospel that is powerless to save. Such errant teaching leaves people with a false hope of salvation and, in a way, inoculates them from the true message. People who are deceived into thinking everything is fine will be more resistant to the truth..." from article: What Does it Mean to Test the Spirits?