The threefold nature of mankind reflects, to a degree, the triune nature of the Godhead. Just as each member of the triune God is complete and wholly God, yet distinct, so each aspect of mankind is also the whole, yet distinct. The body of man comprises the entire man, yet he also possesses certain soulish emotions, desires, and propensities; and finally, the total man is endowed with a spiritual, eternal nature, somehow reflecting the image of God.
These three reflect the three great creative acts of God during creation week, identified by the three usages of the Hebrew word bara, or create. "In the beginning God created the heaven and the earth" (Genesis 1:1); i.e., physical material. Later, certain of this physical material was granted consciousness (1:21), which man shares with animals. On the sixth day, man was created as a spiritual being "in the image of God" (1:27), setting him qualitatively distinct from the animals, though he shares body and consciousness with the animals.
As in our text, when the "God of peace" sets about the task of sanctifying representatives of sinful, fallen mankind, restoring such ones to a measure of Christ-likeness, He does so in the order mentioned, beginning with a spiritual awakening. Then, through the transformed spirit, the soul is reached, and finally the body, with its appetites and lusts.
The wisdom of man says just the opposite, claiming the inner man can be improved by changing outside influences, a mentality all too often reflected even in evangelistic efforts. God's way is to start with the inner man--the root of the problem--and then affect the outer man. JDM