What type of knowledge and control does the enemy (Satan/demons) have? Can they know a believer's thoughts, and then control circumstances to influence their actions?
Scripture seems to suggest that the enemy can influence a believer's emotions and may also influence thinking in some ways. Nevertheless, the enemy’s power (no matter the degree) is always under the authority of God. The enemy does only what the Lord permits, and therefore the enemy's ability to influence a believer’s thoughts or actions is limited to what the Lord allows as a test of the believer for our spiritual good.
The Bible says the Lord allows these tests for our good, but never to tempt or encourage us to sin. Therefore, if the enemy's tests should succeed in causing us to stumble, then we are at fault for willingly following the enemy’s temptations or falling to the enemy’s deceptions through circumstances.
As scripture teaches:
The believer who is earnestly seeking to know and obey the Lord’s will through His Word and in prayer, will not miss the Lord’s instructions nor be forced into falling for the enemy’s schemes. The Lord is more than capable of making His will known to His children, and He promises to equip us - sufficient to ensure our success in the face of such trials. Since the enemy is always under the Lord’s authority, the enemy cannot interfere with the Lord’s communication nor can he trick us into disobedience. Our failures are always the result of willing disobedience to the Word of God.
On the other hand, the Lord may use the enemy to test our hearts, but the Lord promises that we will not be tested beyond our ability to obey. Therefore, if a believer follows after the enemy’s schemes, he or she has willingly departed from what they have heard. Their fall into sin isn’t the result of confusion but is willful disobedience (even though we like to tell ourselves that it wasn’t our fault or “the devil made me do it”). In reality, the believer is guilty of separating himself from God’s will. While the enemy may be part of the situation, he can only stumble a believer who is already failing to listen or is already inclined to disobey the Lord.
The antidote to such confusion and temptation is to remain close to the Lord in His Word and in prayer. Such a believer will be in a strong position to know and follow the Lord’s will even in the face of the enemy’s schemes.
Finally, we are not called to discern the Lord’s will through circumstances exclusively (if at all). Certainly, the Lord may use life circumstances to confirm what He has already told us through His Word and by His Spirit in prayer, but these events are not replacements for an abiding reliance on His Word and prayer. A believer who relies on circumstances, “coincidences,” etc. is ripe for a fall, since the enemy is the prince of the power of the air and he has the world at his disposal.
Again, believers who are sincerely seeking the Lord’s will cannot be stumbled by the enemy in this way, though they may be tested from time to time. Believers who fall to the enemy’s schemes because they failed to heed God’s word or seek His counsel in prayer are always to blame for their own sin.
For more on this topic, we recommend you listen to Pastor Armstrong’s teaching on John 17.