Satan has already deceived a great number of people in the world by blinding their minds to the truth of the gospel, but we must realize that Satan can’t blind just anyone. He can only deceive those who allow themselves be deceived, people who reject the truth.
Paul declared that unbelievers are “darkened in their understanding” (Eph. 4:18) and ignorant, but he also revealed the root reason for their darkened understanding and ignorance:
That you walk no longer just as the Gentiles also walk, in the futility of their mind, being darkened in their understanding, excluded from the life of God because of the ignorance that is in them, because of the hardness of their heart; and they, having become callous, have given themselves over to sensuality, for the practice of every kind of impurity with greediness (Eph. 4:17b-19, emphasis added).
The unsaved are not just unfortunate people who have been sadly tricked by Satan. Rather, they are rebellious sinners who are willfully ignorant and who want to remain deceived because their hearts are so hard.
No person has to remain deceived, as your own life proves! Once you softened your heart toward God, Satan couldn’t keep you deceived.
Ultimately, Satan will be bound during the thousand-year reign of Christ, and he will then have no influence on anyone:
And he [an angel] laid hold of the dragon, the serpent of old, who is the devil and Satan, and bound him for a thousand years, and threw him into the abyss, and shut it and sealed it over him, so that he should not deceive the nations any longer, until the thousand years were completed; after these things he must be released for a short time (Rev. 20:2-3).
Note that before Satan’s incarceration he “deceived the nations,” but when he is bound he will no longer deceive them. Once released, however, he will deceive the nations again:
And when the thousand years are completed, Satan will be released from his prison, and will come out to deceive the nations which are in the four corners of the earth…to gather them together for the war….And they came up on the broad plain of the earth and surrounded the camp of the saints and the beloved city, and fire came down from heaven and devoured them (Rev. 20:7-9, emphasis added).
Why will God release Satan for this short period of time? The reason is so that all those who hate Christ in their hearts but have been feigning obedience to Him during His rule will be manifested. Then they can be rightfully judged. That will be the final test.
For the same reason, Satan is permitted to operate on the earth now—that those who hate Christ in their hearts might be manifested and ultimately judged. Once God no longer has any use for Satan to fulfill His divine purposes, the deceiver will be cast into the lake of fire to be tormented there forever (see Rev. 20:10).