The four levels of personhood by degree of completeness are:
Human Personhood 1
Personhood depends on appearance
If Level 1 is what we are living for, a person will be defined as a physical, material being who is meant to enjoy pleasure and avoid pain. If someone does not look a certain way, or lacks certain physical function, or cannot experience certain pleasures, we may think he or she is not a person.
Human Personhood 2
Personhood depends on ability to achieve
Happiness Level 2 is concerned with ego-gratification, being independent, accomplished, successful, powerful, in control, admired, and popular. In order to be fully human, a person has to have the potential to achieve all, or at least some of these subjective things. This calls into question the personhood of the unborn, the elderly, the disabled, the socially marginalized, the poor, the terminally ill, and other vulnerable populations.
Human Personhood 3
Personhood depends on the potential to give and receive love.
Happiness 3 is commitment and contribution to the good, so a human person is someone who can ? participate in the human community by giving and/or receiving love. The unborn, the elderly, the disabled, etc., are all people because they all have the potential to participate in love. But if we leave our definition at Level 3, we risk missing out on the unconditional worth and dignity of human persons, and failing to recognize their eternal destiny.
Human Personhood 4
Personhood is recognized in all humans, because we are made in God’s image.
Level 4 understands the meaning of human life as union with the unconditional love of God. Therefore, any being who can ultimately recognize and receive the unconditional love of God is a person. Since all human beings are made in the image and likeness of God, and therefore created for His unconditional love, all human beings are human persons.
Source: Healing the culture = A unique educational pro-life organization with a mission to change the way people think about life (healingtheculture.com)