Paul was not speaking of a single individual. Because he states that this “man” was evident in his day and would continue in existence until God destroyed him at this system’s end. Thus, he has existed for many centuries. Obviously, no literal man has lived that long. So the expression “man of lawlessness” must stand for a body, or class, of people who opposes God, his purposes, and his people.
Therefore it is vital that we identify this man of lawlessness. Why? Because he is intent on undermining our good standing with God and our hope of eternal life. How? By getting us to abandon the truth and to believe falsehoods in its place, thus diverting us from worshiping God “with spirit and truth.” (John 4:23)