The Bible defines the man of sin as one who makes his own laws in the place of God (2 Thes. 2:1-12). He deceives men as he contradicts the truth. The power to counteract his error is the truth; the gospel of Christ.
Because of the danger and damnation of the man of sin, the New Testament is filled with warnings. Satan and his followers never rest; they continually seek to destroy souls. Our duty is to recognize truth from error and resist the man of sin.