Consider this illustration. A successful military defense often involves several lines of defensive bulwarks. No successful general would feel that any one of these is unimportant and should be given up without a fight. In a Christian’s fight against sin, there are several lines of defense as well.
James 1:14, 15 states that “each one is tried by being drawn out and enticed by his own desire. Then the desire, when it has become fertile, gives birth to sin.” The first step toward sin is the cultivation of a wrong desire in the mind. Thus, the first line of defense is to refrain from cultivating the desire—to control one’s thinking.
It is because of this link between thoughts and actions that the Bible warns us: “Keep your minds fixed on the things above, not on the things upon the earth.” (Colossians 3:2) When Christians refuse to dwell mentally on immorality, spiritism, or apostasy, they make this decision, not because they fear that these ideas might prove superior to Bible truths, but because they wish to avoid anything that could draw them into a sinful course.