What I would like to start investigating and understanding is the role of "person" in ethical thought. Need one start at a theological level to argue for the dignity of a person? Is dignity a transcendental? Must one "start" with a Trinitarian notion of person to understand human personhood and dignity? Can one start there (a prior question)?

The source of personalism is the nature of the human person. We have from tradition (at least) two definitions of “person.” Boethius: persona est rationalis naturae individua substantia—a person is an individual substance of a rational nature. Also, the Roman jurists: persona est sui iuris et alteri incommunicabilis—a person is something in his own right and incommunicable (in-exchangeable or un-sharable) with another.

We can see that a human person has innate dignity by looking at these definitions. Now, dignitatis in Latin can mean dignity, but also worth or rank or office. So tied up with dignity is the idea of hierarchy: one person being better or more worthy than another by rank or office—or in the case of different beings, by being what it is.

Human dignity comes from being rational, from being the sort of thing that has a mind and a heart and therefore can know and love God. This is implied in Boethius’ definition. We as human persons are thus higher and more dignified than beings that cannot know and love God, but less dignified (naturally speaking) as beings that can know and love God in a higher way, i.e. the angels. An angelic person has more dignity than any one of us (naturally speaking).

Human dignity also comes from being irreplaceable or unique. We are each unique creations of God—“the loving gaze of God the Father” continually falls on each of us. This uniqueness is implied in the definition of the Roman jurists: sui iuris et alteri incommunicabilis—one & unique.