Society has made the definition of person ambiguous. We think we know a person when we see one. A man is a person. A woman is a person. A boy is a person, and so on. A technical definition used today is that a person is a being with self-awareness or a being with certain legal rights and responsibilities within a culture. These distinctions presume a more fundamental definition. Are all human beings persons? Are only human beings persons? Who has the final say? We hear arguments that apes or dolphins might be persons because they are intelligent, and then we hear that human embryos and fetuses, better known as unborn children, are not persons. What does it mean to be a person?

The origin of the word person is classical Latin, persona, meaning a mask worn by a character in a play. It came to mean a human being in general. Here’s the cool part for Catholics: the word person was developed by theologians in the early Church trying to understand God. In the Trinitarian and Christological debates of the fourth and fifth centuries, the word was borrowed to articulate what we mean by saying that there is one God in three persons and that Jesus is one divine person with two natures.

In the sixth century a Roman philosopher and Christian martyr named Boethius defined the word person as “an individual substance of a rational nature.” In the thirteenth century, St. Thomas Aquinas, the great integrator of Aristotelian natural philosophy and Christian theology, built on Boethius’s definition in the first part of his Summa Theologiae (ST.I.29.1). You can read there how Catholics used the word “person” to articulate the Holy Trinity. None of our words can fully explain God, of course, but the word person helps the Church teach the doctrine of the Holy Trinity. God is one nature totally possessed by three divine persons. The Father possesses the whole nature of God as his own. The Son possesses the whole nature of God as his own. The Holy Spirit possesses the whole nature of God as his own. Since the nature of a being determines what the person is, the Father is God, the Son is God, and the Holy Spirit is God. They do not share the nature (that is heresy); each wholly possesses it. (See also Catechism of the Catholic Church 255.)

Let’s explore Boethius’s definition. As “an individual substance of a rational nature,” a person has the ability to reason (hence the adjective rational). This power of the soul separates the person from lower animals, which can sense but not reason, and from plants, which live and grow but can neither sense nor reason. Persons also have, according to Aquinas, “dominion over their own actions.” This is what we call the power of free will.

Since a being either has reason and free will or does not, personhood is binary. There are no gradients of personhood. We may call animals intelligent, but we do not mean to say that they can exercise free will and the power of reason. For example, the smartest of dogs (and I love dogs!) could not decide to give up a T-bone steak to a starving child. This requires the practice of virtue, such as charity and temperance. In the created order of beings with bodies, only human beings fit the definition of person.

There is one more category of persons: angels. In his treatise on the angels in the Summa Theologiae, St. Thomas Aquinas, referencing Pseudo-Dionysius, a theologian and philosopher from the late fifth to early sixth century, says that angels are purely intellectual beings or “heavenly minds” (ST.I.58.3). Angels fit Boethius’s definition of person. They are “individual substances,” though without bodies, and they are “of a rational nature,” which is to say they possess intellect and free will. However, because they are not encumbered by bodies, their dignity surpasses that of humans. Intellect for angels is perfect at once “from their very nature.” That means they instantly know all they are created to know. Since the angels who chose goodness apprehend only goodness, they always will what is good. The word “angel” is a another topic itself, but for now, we need to add angels to the list of persons. Let’s go back to the definition of the word person.

This inter-relation among the divine persons has significance for the understanding of human intellect and free will. The Son proceeds from the Father as an act of divine intellect, somewhat like how a word is conceived in the mind. The Son is the Word, the Logos. From the Father and Son together as one substance, the Holy Spirit proceeds as an act of divine will. The three persons are in perfect, eternal communion.

Because we humans are created in God’s image and likeness (Gen. 1:27), we have the Trinitarian spiritual powers of intellect and will, though not perfectly, which instill in us the natural reciprocal desires to know and be known, to love and be loved. This desire for communion means we are made to learn, think, and make choices, to seek what is good and abhor what is evil. We also naturally desire to belong to our families and communities—many persons united as one entity. The more people freely give, receive, and search for good, the more they are united, the more they learn, the more humanity progresses. This is what it means to be human.

So when the Catechism says that the “divine image is present in every man” and that this image “shines forth in the communion of persons, in the likeness of the unity of the divine persons among themselves” (CCC 1702) the Church is affirming the revelation that man is made in the image and likeness of God. Our goal in this mortal life is to attain the happiness of being united with the Holy Trinity—with the unity of divine persons after which we have been fashioned—in eternity. We are made for it.

Recognizing this holy purpose puts human life in a lofty context. Human persons are not mere clumps of cells but images of God destined for everlasting communion with him, even the tiniest of human embryos. Scientific research and technology must safeguard the great dignity with which God has endowed mankind. For the nonbeliever or anyone who does not grasp the significance of the definition of person in the context of God the Creator, a person can be anything anyone opines, which is why there are so many bioethical issues today, such as abortion, using fetal tissue for research, in vitro fertilization, embryonic stem cell research, and cloning. In this ambiguous lack of definition, a human person is, and is worth, whatever some other humans decide. Not so for Catholics. We understand the human person as made in the image and likeness of God, and we are to defend the sanctity of human life. Teach others the true meaning of the word!

God, grant me the grace to be who I am meant to be.

By Stacy A. Trasancos

Stacy A. Trasancos, PhD Stacy Trasancos worked as a senior research chemist for DuPont before converting to Catholicism, then left her career to stay home with her highly complex composite systems who call her Mommy. She studied dogmatic theology and in those years became a writer and educator. Dr. Trasancos served from 2018 to 2022 as the Executive Director of the St. Philip Institute. She and her husband, Jose, now operate Children of God for Life, an organization that fights to end the use of aborted children in research. She is also a Catholic author, speaker, and educator. Read more about here work on her website,