How is the human soul different from his spirit?

Is man dual or tripartite in nature? If the latter, how are spirit and soul distinguished?

Certainly tripartite, as 1 Thessalonians 5:23 proves—”I pray God your whole Spirit and Soul and Body be preserved’ blameless unto the coming of our Lord Jesus Christ.” An attempt was made by the late Dr. Bullinger to shew that man is dual:—the combination of Spirit and Body forming the Soul—but it was clearly untenable, for if that were the case, the order of the words would be Spirit and Body, even the Soul; and at death the personality would be dissolved, a doctrine even worse than the so-called “sleep of the soul.” The Spirit and the Soul represent the spiritual side of man, which is sometimes called by one name, sometimes by the other.

They are distinct, but only divisible in a metaphorical sense by the Word of God “piercing even to the dividing asunder of soul and spirit” (Hebrews 4:12), that is, they are never viewed as separated one from the other. The Spirit is the higher part; with it, man understands (1 Corinthians  2:11), and is in touch with the unseen :—“God is Spirit: and they that worship Him must worship Him in spirit and in truth” (John 4:24). The Soul is the other side of man’s spiritual being, and links it with the body—it desires, loves, sorrows, etc. “My soul is cast down within me” (Psalm 42:6; see also 1 Samuel 18:1; Numbers 21: 4; 2 Samuel 5:8).

The personality is sometimes connected with the soul (e.g., “few, that is, eight souls* were saved by water”), or with the body. When Stephen fell asleep, we read that “devout men carried him (i.e., his body) to the burial” (Acts 8:2), but Stephen in a higher sense was not in the graveyard, but with Him to Whom he had just committed his spirit.”