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:
James 1:2 Consider it all joy, my brethren, when you encounter various trials,
James 1:3 knowing that the testing of your faith produces endurance.
James 1:4 And let endurance have its perfect result, so that you may be perfect and complete, lacking in nothing.
1Cor. 10:12 Therefore let him who thinks he stands take heed that he does not fall.
1Cor. 10:13 No temptation has overtaken you but such as is common to man; and God is faithful, who will not allow you to be tempted beyond what you are able, but with the temptation will provide the way of escape also, so that you will be able to endure it.
2Pet. 2:9 then the Lord knows how to rescue the godly from temptation, and to keep the unrighteous under punishment for the day of judgment,
1Pet. 4:19 Therefore, those also who suffer according to the will of God shall entrust their souls to a faithful Creator in doing what is right.
1Pet. 5:8 Be of sober spirit, be on the alert. Your adversary, the devil, prowls around like a roaring lion, seeking someone to devour.
1Pet. 5:9 But resist him, firm in your faith, knowing that the same experiences of suffering are being accomplished by your brethren who are in the world.
1Pet. 5:10 After you have suffered for a little while, the God of all grace, who called you to His eternal glory in Christ, will Himself perfect, confirm, strengthen and establish you.
2Tim. 4:17 But the Lord stood with me and strengthened me, so that through me the proclamation might be fully accomplished, and that all the Gentiles might hear; and I was rescued out of the lion’s mouth.
2Tim. 4:18 The Lord will rescue me from every evil deed, and will bring me safely to His heavenly kingdom; to Him be the glory forever and ever. Amen.
2Th. 3:3 But the Lord is faithful, and He will strengthen and protect you from the evil one.
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.