Trichotomy holds that humans are composed of three parts: body, soul, and spirit. Franz Delitzch and Watchman Nee were advocates of this view. Under this view, humans have a spirit in addition to their soul that comes alive at conversion. Thus Paul writes, “If Christ is in you, though the body is dead because of sin, yet the spirit is alive because of righteousness” (Rom. 8:10).
The problem with trichotomy is that the words “soul” and “spirit” are used interchangeably throughout Scripture. Jesus says that his soul is trouble (Jn. 12:27), but a few verses later, we read that he became “trouble in spirit” (Jn. 13:21). Likewise, Jesus mother says, “My soul exalts the Lord, 47 And my spirit has rejoiced in God my Savior” (Lk. 1:46-47). Moreover, dead believers can either be called “spirits” (Heb. 12:23) or “souls” (Rev. 6:9; 20:4). At death, either the “soul” departs the body (Gen. 35:18; 1 Kings 17:21; Isa. 53:12; Lk. 12:20) or the “spirit” departs (Lk. 23:46; Eccl. 12:7; Jn. 19:30; Acts 7:59). The “spirit” knows an individual (1 Cor. 2:11); therefore, the soul and spirit perform the same function.
Passages in Support of Trichotomy
(1 Thess. 5:23) Now may the God of peace Himself sanctify you entirely; and may your spirit and soul and body be preserved complete, without blame at the coming of our Lord Jesus Christ.
(Heb. 4:12) For the word of God is living and active and sharper than any two-edged sword, and piercing as far as the division of soul and spirit, of both joints and marrow, and able to judge the thoughts and intentions of the heart.
(1 Cor. 14:14) If I pray in a tongue, my spirit prays, but my mind is unfruitful.
These are simply cases where the author is using synonyms for effect. If we pressed these too much, we would have to affirm more than three parts, but actually four, as in the case of Mark 12:30.