You speak to other people and you speak to yourself in your mind. You have imaginary conversations and even arguments with others within your mind. You think your mind is private and only you are generating the thoughts and initiating the conversations. You think you are conversing only with yourself, like one who plays a game of chess with himself controlling both sides of the board. This is not the Truth. Your thoughts are not hidden behind an impenetrable, sound-proof, and private room. Any spirit can hear and join your thoughts. He will use your thoughts to speak to you. Do not be fooled. Your thought-life is not a private conversation with yourself alone.
Proverbs 4:23 Be careful how you think; your life is shaped by your thoughts.
1 John 4:1 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.
Romans 8:7 Because the carnal mind is enmity against God; for it is not subject to the law of God, nor indeed can be.
Ephesians 6:11-12 Put on the whole armor of God, that you may be able to stand against the wiles of the devil. For we do not wrestle against flesh and blood, but against principalities, against powers, against the rulers of the darkness of this age, against spiritual hosts of wickedness in the heavenly places.
1 Peter 5:8 Be sober-minded and alert. Your adversary the devil prowls around like a roaring lion, seeking someone to devour. 9 Resist him, standing firm in your faith and in the knowledge that your brothers throughout the world are undergoing the same kinds of suffering. 10 And after you have suffered for a little while, the God of all grace, who has called you to His eternal glory in Christ will Himself restore you, secure you, strengthen you, and establish you.
2 Corinthians 10:5 We tear down arguments, and every presumption set up against the knowledge of God; and we take captive every thought to make it obedient to Christ.
Ephesians 6:11-12 Put on the whole armor of God, that you may be able to stand against the wiles of the devil. For we do not wrestle against flesh and blood, but against principalities, against powers, against the rulers of the darkness of this age, against spiritual hosts of wickedness in the heavenly places.