The Reality of Spiritual Warfare

Whatever is not of God is of the enemy. We need to understand our enemy and the victory we have in Christ Jesus. He made an open display of defeating Satan at the cross.
Peter gives us a description of the devil so that we can discern who he is, his activities and the way he works.
If you are saved today you have the ability, through the Holy Spirit, to try every spirit to see if they are of God. You try every spirit by the truth of the Word of God.