"Now concerning that day or hour no one knows—neither the angels in heaven nor the Son—except the Father.” (Mark 13:32)
Angels and demons are limited in their knowledge. Unlike God, who is omniscient (all-knowing), the extent of knowledge possessed by these created beings is finite. This passage tells us that even the angels don’t know the day when Jesus will return. (It is important to note here that Jesus is speaking. So when He says that even the Son doesn’t know the day or hour, it means that God had not revealed it to Him in his physical form. The Father, Son, and Holy Spirit are all God, and as such are equally all-knowing. However, when Jesus came to earth, he chose to function in the limited knowledge of a human.)
So, we see here that angels and demons do not know the future. Likewise, consider the implications of this passage from Daniel on the ability of demons (the power behind mediums, diviners and such) to read someone’s mind. Daniel’s is addressing the king of Babylon’s demand that his advisors tell him both what he had dreamt and what it meant.
Daniel answered the king: "No wise man, medium, diviner-priest, or astrologer is able to make known to the king the mystery he asked about. But there is a God in heaven who reveals mysteries, and He has let King Nebuchadnezzar know what will happen in the last days. Your dream and the visions that came into your mind as you lay in bed were these: (Daniel 2:27-28)
Daniel told the king that no created power could read the king’s mind to discover the contents of his dream. However, God, who knows our thoughts (Ps. 94:11), was more than capable of revealing to Daniel both what the king had dreamt and the future it foretold.
It is important to note that while angels and demons are not all-knowing and can’t foresee the future, they have been around for millennia and have observed humanity for just about as long. There are people who are very skilled in reading other people. They can give the perception of mind-reading. How much more so beings who have had thousands of years to study people. Be aware that the enemy is most capable in deception whether in making highly educated guesses about what someone is thinking, or in predicting the future and then acting to bring about that future.
Here is an example from In The Image of Man where a demon gives his charge, Mayor Trenton Richards, awareness of things the mayor should have no way of knowing.
“Oh, I know a lot of things—more than you might think,” Trenton said. “Perhaps you have not realized, Sergeant Davis—I am a psychic. I know all kinds of things I should have no way of knowing.” He bobbed his head. “I mean sure, I know about your attraction to Sarah and your friendship with Daryl. The real reason you are looking for someone to blame. But Marge down at the diner knows these things.” Trenton shook his head. “No, this is not the type of knowledge that proves I’m psychic.” He picked up his pen and tapped on the pad of paper. “Now, knowing that Fred Johanus was having an affair with Mrs. Freeman, and leaking it to the press, just in time to ensure I got elected Mayor, that is a different story. Or perhaps closer to home, how about knowing you were ready to ditch your sweet relationship with Ms. McIntyre for a spicy dish from your past—Leilah at Francisco’s?”
Chris’ stomach tightened.
“Ah, I see you are beginning to understand.”
Anyone who does these things is detestable to the Lord. The words from Deuteronomy echoed in Chris’ spirit. – In The Image of Man