Modalism
The view that Father, Son and Spirit are three modes or presentations of a single person rather than three distinct persons. The early Church rejected it, and it matters here because collapse into modalism is the direction any purely structural argument for the Trinity falls in when it fails.
Modalism holds that the one God appears in three ways — as Father in creation, Son in redemption, Spirit in the Church — and that Father, Son and Spirit are not three distinct someones but three presentations of one. The early Church rejected it, most sharply because it makes the Son's prayer to the Father a performance.
It matters in this material because it names a direction of failure. When an argument for the Trinity rests only on structure, and structure turns out not to individuate its occupants, the result is not three persons and it is not four. It is one occupant filling three roles — which is modalism, arrived at by accident.
Where this comes up
Sources
- Debby research packet OTC-002, on structural collapse