Believing you know the truth is like me believing satan knows the truth, which I don't believe
But it was short lived. And THAT is when satan realized THE TRUTH. When Christ arose from the dead. That is when satan discovered that he had tricked HIMSELF by crucifying Christ- that God had actually PAID FOR MAN'S SINS by the death of Christ. That is the good news of the Cross that Paul proclaimed. That God had sent him forth to offer "redemption through His blood, the forgiveness of sins, according to the riches of His grace" (Eph. 1:7).
Satan reached the climax of his career of deception when he deceived HIMSELF at Calvary.
"But we speak the wisdom of God in a mystery, even the hidden wisdom, which God ordained before the world unto our glory: Which none of the princes of this world KNEW; for HAD THEY KNOWN IT, THEY WOULD NOT HAVE CRUCIFIED THE LORD OF GLORY." 1 Cor. 2:7-8.
Satan KNOWS the truth. He KNOWS his time is short. He KNOWS his defeat was at Calvary. That is why he hates and opposes the message of grace, the preaching of the cross, more bitterly than he ever hated or opposed the prophetic program. Nor is it strange that it is GOd's purpose:
...that NOW unto the principalities and powers in heavenly places might be known by the church the manifold wisdom of God." (Eph. 3:10).
If you don't believe he knows the truth, you are deceiving yourself and being deceived.