I’ve often heard it said that Satan cannot read minds. The reason, people say, is that it is because he is a created being. But that is no real answer. Since Satan was created by God, seems to me that God could have given him whatever abilities He wanted to, even knowing thoughts. Frankly, though, in most cases, Satan’s intelligence gathering demonic ‘network’ is very likely so efficient that he might seem to know thoughts. So, can Satan know our thoughts or not, and, if not, what is the biblical reason for that stance?
There’s no Biblical evidence to support the claim that Satan can read thoughts, so the consensus among scholars is that he can’t. There’s no way of knowing how many helpers he has so it is possible that he can spy on a great many people. Obviously he doesn’t need to worry about unbelievers, and even most Christians have such a strong secular world view that they pose little or no threat to him. That leaves the relatively small number of truly “sold out” Christians for him to keep track of. It’s probably not as big a job as we think.
He’s also been around a very long time and he’s very bright so he’s seen and heard just about everything by now and is likely pretty good at predicting what we’ll do in a given circumstance. And by influencing our leaders in government, education, entertainment, etc, he can have an astonishing influence on our culture with comparatively little effort. The fact that we’re all fallen sinners gives him further advantage.
Personally, I believe that he can plant thoughts at the threshold of our minds that we can either accept or reject. I think 2 Cor. 10:3-5, Ephes. 6 and other passages were written to help us defend against this kind of attack.