One of the helpful things about philosophy is that it can take commonsense things that we know intuitively and formalize them into definitions with distinctions.

Take the question, “Who are you?”

We would answer this in terms of those properties—attributes, qualities, characteristics—that make me who I am as an individual. We often answer this identity question by pointing to our relationships (firstborn son of my X and Y; husband of Z; father of A, B, and C) or our physical characteristics (think driver’s license: address; certain height and weight; color of skin, hair, eyes).

A less common question, but one quite relevant for theology, is “What are you?” With regard to persons, this is getting at the kind of being that one is. This can be called a “kind essence”—the set of properties (or collection of characteristics) sufficient to establish one’s membership in a certain “kind” of being (e.g., God, angel, human, animal, etc.).

There is also a difference between “common properties” and “essential properties.”

Common properties would be the sort of qualities that most people in that kind or category would have.

Essential properties would be the things that every member of that category has to have—such that to lack one of these properties is not to be a member of this kind.

A common property of being a human being might be “having two arms and two legs.” It’s a true characteristic in most cases. But obviously an amputee is still a human being, therefore we know it’s not an essential property. Properties like “having a human soul” would be in a different category. All living human beings have human souls, such that the absence of a human soul would mean that the being is not a human being.

There are some properties that might give us a bit more pause. For example, we say “to err is human.” But if we’re operating from a biblical worldview we know that this is true for all of us who have inherited Adam’s sin—but it’s not necessarily true for the category “human being” per se. Or take the property “being the biological product of two parents.” Again, it’s true for almost every human, but it is not a necessary property, as a human clone would still be a human being.

Believe it or not, this is not merely fun philosophical slicing and dicing. It actually can help us to think about Jesus as God Incarnate, the God-Man.

Here’s a simple chart (courtesy of Fred Sanders) summarizing Chalcedonian orthodoxy on the person of Jesus:

Let’s take our second question above, “What are you?” and apply it to Jesus.

On the one hand, he (like all human beings), belongs to the natural kind of humanity. Even if he is not merely human, he is fully human. He has all the essential properties required for full humanity.

On the other hand, he belongs to the natural kind of divinity. He lacks no essential property or attribute required for him to be fully God.

What about the question “Who are you?” This is asking about Jesus’ individual essence. If we understand this to be the essential properties that make him who he is, then we would want to include his divine kind-essence—his fully-God nature—for those cannot be lost without him ceasing to be the Son of God. Jesus’ human kind-essence, on the other hand, is contingent. It is not something he had forever. And if he had never become incarnate, he still would remain God’s Son.

So in everyday language, we could paraphrase the conclusion of Chalcedon as saying that Jesus is “one who” (one person), with “one what” (fully divine nature), who took on “another what” (fully human nature) in the incarnation—such that he is now “one who” (one person) with “two what’s” (two natures).

In so doing, Chalcedon insisted, these “two what’s” experience “no confusion, no change, no division, no separation.”

Now this raises another question. How should we talk about qualities that would apply to only one of Jesus’ natures? For example, “existed from all eternity” applies to his divine nature, not his human nature; “was tired” applies to his human nature, not his divine nature.

The Italian theologian Peter Martyr Vermigli (1492-1562) gives the right answer:

Christ Jesus is one person in whom the two natures subsist in a way that they are joined with each other so that they cannot in any way be pulled apart from each other.

Therefore all the actions of Christ should be attributed to the hypostasis or person because the two natures do not subsist separately and by themselves; neither do they act separately as if one nature is said to do some certain work but the other nature something else.

Therefore just as the [two natures] have one hypostasis or experience, so every work of Christ of any sort should be ascribed to the hypostasis or person itself.

Meanwhile the properties of the two natures which are in Christ should be kept distinct, whole and unmixed so that they cannot in any way be confused. Hence when Christ is said to have been born of the Virgin Mary, been wounded, died, and buried and taken up into heaven—all these things assigned to the person itself in which the two natures exist, but insofar as he was a man, not as God. The divine nature does not allow these changes and sufferings. Again when it is said that Christ is the creator of heaven and earth, that he was before Abraham existed, even that he exists from eternity and is everywhere—these are to be understood of the person or hypostasis, but insofar as it was God, not as a man. For such things are not proper for a created and finite nature.

(“A Letter to Poland,” in The Peter Martyr Reader, pp. 127-128.)

In all of our analysis, let us remember that our goal should always be for these doctrines to terminate on wonder and worship of the Incarnate God:

Infinite and yet an infant.
Eternal and yet born of a woman.
Almighty, and yet nursing at a woman’s breast.
Supporting a universe, and yet needing to be carried in a mother’s arms.
Heir of all things, and yet the carpenter’s despised son.”

—Charles Haddon Spurgeon

That man should be made in God’s image is a wonder,
but that God should be made in man’s image is a greater wonder.
That the Ancient of Days would be born.
That He who thunders in the heavens should cry in the cradle?”

—Thomas Watson

Man’s Maker was made man
that the Bread might be hungry,
the Fountain thirst,
the Light sleep,
the Way be tired from the journey;
that Strength might be made weak,
that Life might die.


And the Word became flesh and dwelt among us,
and we have seen his glory,
glory as of the only Son from the Father,
full of grace and truth.”
(John 1:14)

Thanks to James Anderson and Steve Wellum for providing helpful comments on an earlier draft of this, and Chris Castaldo for pointing me to the Peter Martyr quotation.