Biblically, I think it's difficult to come up with a complete schematic of the human person. Scripture uses a lot of different terms to describe aspects of what being human is.
Yes, the Bible was written over a long period and by many authors who used the same terms in different ways. The consistency issue is further complicated by Church Fathers who were unfamiliar with Biblical Hebrew and affected by Plato's views. But the Wikipedia article I referenced has a long list of patristic writers who believed in Trichotomy. And the Apostle Paul believed that the soul and the spirit were separate (and connected) parts:
1Th 5:23 Now may the God of peace himself sanctify you completely, and may your whole spirit and soul and body be kept blameless at the coming of our Lord Jesus Christ.
Heb 4:12 For the word of God is living and active, sharper than any two-edged sword, piercing to the division of soul and of spirit, of joints and of marrow, and discerning the thoughts and intentions of the heart.
Paul's trichotomy was based on the Shema's 3 elements of man:
Deu 6:4 “Hear, O Israel: The LORD our God, the Lord is one. 5 You shall love the LORD your God with all your heart and with all your soul and with all your strength.
לב /
Kardia (heart). נפׁש (nefesh) /
Psyche (soul). מְאֹד /
Ischys (strength)
For example when Scripture speaks of the heart, we know that's not literally speaking about the blood-pumping organ in our chest, but is speaking to that part of us that feels, something core within us. The is the heart part of the soul, the spirit, or something different?
The glossary of the Philokalia defines the heart as "the spiritual center of man's being." It also acknowledges that that is not the only definition used in the Bible.
What is the mind? Scripture describes us as comprised of many things.
Modern people tend to talk about the body, mind, and consciousness. In the NT, there are 2 words commonly translated as mind: nous (consciousness) and dianoia (understanding).
I tend to reject trichotomism because I believe it insists on a hard dichotomizing of soul and spirit, something that I simply don't think Scripture supports.
I agree that a hard dichotomizing of soul and spirit is not called for. As human beings, our 3 parts are interconnected.
I think biblical language is actually both a lot more fluid than that, as well as more amiguous. I think the safest position is a dichotomism that recognizes that the human creature is an amalgam of material and immaterial; that we are fully material creatures but that there is an immaterial dimension to our existence. That is to say, we aren't just bodies. Terms like "soul" and "spirit" address, in different ways, aspects of that trans-material reality of being human.
Perhaps the difference between your view (that the soul and the spirit are a single unit) and my view (that they are two connected parts) is after physical death.
In your view, the soul/spirit survives death.
According to my view, the soul and spirit are separated at death. I think this is consistent with Paul's teaching:
1Co 15:44 It is sown a soulish body; it is raised a spiritual body. If there is a soulish body, there is also a spiritual body.
This view supports both soul sleep (like Luther's) and the conscious life of the human spirit (rational soul).