The doctrine of the Trinity has been a part of orthodox belief since very early in the church. I find it interesting that how many parts man has is still an open question. It does not receive much attention lately, largely because we fail to see the implications of how we view ourselves. Great thinkers throughout history have weighed in on this topic, but I’m not going to attempt a philosophical or theological overview or argument here. I want to offer some personal experience as an explanation for my preference for a tri-part understanding of human nature.
I should really start by acknowledging that there are various tri-part theories. This is not merely a debate between a single 2-part and a single 3-part construct. To clarify, my general view of a tri-part human nature is body, mind, and spirit. Body is fairly obvious — our flesh and bones. Mind is a bit more numinous, but is centered on our intellect and has something to do with that part of our body we call our brain. Spirit is a deeper ontological piece, something that endures even at the destruction of body or mind.
I hold to this view for two reasons. One is theological. We are created in God’s image and God is Trinity. In the Father we have a parallel to our mind, our will. In the Son we have the incarnation, his body and blood. In the Holy Spirit we have an ongoing and more mysterious member that is nevertheless undoubtedly God.
My other reason for clinging to a tri-part view is pastoral. Over the years I have witnessed various people who have lost their minds in some form or fashion from the effects of aging, medication, or disease — like Alzheimer’s or the brain disorder that killed my mom. In such situations, we witness a loss of a significant part of the person. Mental acuity and memory disappear and we are left wondering where they went. Their body is still before us but we struggle with the loss of their minds and we may worry about the state of their soul before God, especially if we hold an evangelical view of justification.
But if we allow the possibility that there is also a spirit, a soul, that holds an essential part of the person, we can accept the loss of the mind (and eventually body) with comfort that the spirit carries on. This continued presence, even before death, indicates to us that sacramental acts can still be efficacious even if there is not mental assent on the part of the one who is ill.
This view has implication on the other end of life as well. Not only does it provide comfort and hope when the mind is slipping away, but also before it has formed. A child in the womb grows a brain during the nine months in utero. When they are born, they are not very adept at using it yet, so it takes years before their mind reaches full functioning. And for some children, it never does, either through genetic or disease caused hindrances.
They still have a spirit — or soul, if you prefer. There is still something that is them that will endure throughout their life and beyond. There is still this component of being that we believe is altered (in addition to body and mind) in baptism and through the Eucharist. The idea of a spirit that is distinct from but related to our mind and body has important ramifications for our pastoral care and our sacramental theology. In a society that would increasingly tell us we are only body, that we are just biological machines, it is an important idea to reinforce.