Heidelberg Catechism Q. 18: One Mediator, Two Natures

The Definition of Chalcedon (451)

We, then, following the holy Fathers, all with one consent, teach men to confess one and the same Son, our Lord Jesus Christ, the same perfect in Godhead and also perfect in manhood; truly God and truly man, of a reasonable soul and body; consubstantial with the Father according to the Godhead, and consubstantial with us according to the Manhood; in all things like unto us, without sin; begotten before all ages of the Father according to the Godhead, and in these latter days, for us and for our salvation, born of the Virgin Mary, the Mother of God, according to the Manhood; one and the same Christ, Son, Lord, Only-begotten, to be acknowledged in two natures, inconfusedly, unchangeably, indivisibly, inseparably; the distinction of natures being by no means taken away by the union, but rather the property of each nature being preserved, and concurring in one Person and one Subsistence, not parted or divided into two persons, but one and the same Son, and only begotten, God the Word, the Lord Jesus Christ, as the prophets from the beginning [have declared] concerning him, and the Lord Jesus Christ himself has taught us, and the [Nicene] Creed of the holy Fathers has handed down to us.


Even before the end the apostolic era (90s AD) the New Testament church faced a serious challenge from a group of people who  professed faith in Jesus but who denied the reality of his humanity. This problem is reflected in Apostle John’s language in 2John 7, “For many deceivers have gone out into the world, those who do not confess the coming of Jesus Christ in the flesh. Such a one is the deceiver and the antichrist.” This heresy, the denial that Jesus is truly human, caused a schism in the church. We see it in 1John 2:18-19,

Children, it is the last hour, and as you have heard that antichrist is coming, so now many antichrists have come. Therefore we know that it is the last hour. They went out from us, but they were not of us; for if they had been of us, they would have continued with us. But they went out, that it might become plain that they all are not of us.

According to John, this heresy has far reaching implications.

Who is the liar but he who denies that Jesus is the Christ? This is the antichrist, he who denies the Father and the Son (1John 2:22-23).

An attack on Jesus’ humanity is a denial of Jesus’ as Messiah and that is a denial of “the Father and the Son.” In other words, Christian truth and salvation hang together. These “antichrists” also argued that “Jesus is not from God.” They have the “spirit of the antichrist…” (1John 4:3).

The Patristic church battled various forms of denials of Jesus’ humanity. Some of them simply asserted a dualism (what Peter Jones calls “two-ism”) of being, that there are two kinds of being, one inferior and one superior that exist on a continuum or a ladder. Spirit was said to be at the top of the ladder and matter (creation) at the bottom. These dualists  denied that Jesus’ humanity was real. They knew a priori (i.e., before they knew anything else) that it could not be real. Jesus only seemed to be human. They had a “docetic” (from the Greek verb “dokeo” to seem) Christology.

Some built on this dualism in the second century (the 100s) to assert that not only did Jesus only seem human but what humans need is salvation from lack of being via secret knowledge to which, they claimed, they alone had access. These were the Gnostics. They divided humanity into those who had this knowledge, ordinary Christians, and those who had no idea about a transcendent truth. They taught an increasingly complex hierarchy of being. They regarded Yahweh as the “god” of the OT and as an inferior deity. They knew a priori that Yahweh could not be “the” God. They regarded creation (matter) as evil, something to be overcome.

This sort of rationalism (setting reason as an authority outside of God’s Word and above God’s Word) would not only trouble the church from without but also from within, who would have trouble holding and confessing that Jesus is true God and true Man.

Some of them knew a priori that God’s oneness was such that Jesus was only an attribute of the Father (dynamic monarchianism) or that God manifested himself in three distinct modes of being (Father, Son, and Holy Spirit). These Monarchians usually also taught that Jesus was a godly man who was adopted into the deity. Hence this view was known as adoptionism.

There were others who taught that there Jesus had not two natures and one person but two persons. Nestorius and his followers were accused of this heresy. Their opponents, the Eutychians, taught that Jesus had only one nature.

The Definition of Chalcedon (451) was adopted to address the confusion of the natures.

Next time, the Reformation debate over the natures.

    Post authored by:

  • R. Scott Clark
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    R.Scott Clark is the President of the Heidelberg Reformation Association, the author and editor of, and contributor to several books and the author of many articles. He has taught church history and historical theology since 1997 at Westminster Seminary California. He has also taught at Wheaton College, Reformed Theological Seminary, and Concordia University. He has hosted the Heidelblog since 2007.

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  1. Thanks Scott for the helpful Christological summaries. I hope you flesh out the Lutheran vs Reformed views and their sacramental implications.

  2. Thank you for this great teaching. We need to be reminded of this over and over again, so that we can teach it to others.

    I look forward to the rest of the series!

  3. Nestorius felt vindicated by Chalcedon. Today, you’ll hear Orthodox and RC theologians (and even evangelical writers) state plainly that “Nestorius was not a Nestorian”.

    His “one prosopon after the union” theology posited a weaker “union” than Cyril’s theology (which had been “adopted” at Ephesus but which was modified at Chalcedon) eventually led to the schism of the followers of Cyril, who became the “monophysites” (“one nature” — who are the modern-day Coptics in Egypt).

    I know there are “flavors” of these theologies, and later councils moved away from Chalcedon precisely because it seemed “too Nestorian”.

  4. Dr. Clark, when you say Nestorius and his followers were accused…, are you suggesting as noted in a previous comment that Nestorius was not a Nestorian?

    • I’m not taking an historical position but only recognizing that contemporary scholarship has raised doubts about the traditional story. Certainly his contemporary critics thought he was teaching what has been traditionally attributed to him.

  5. Dr. Clark, as you know, it becomes a semi-practical matter in terms of our attitude toward the extant Oriental Church. I’ve been pondering the question since reading some of the histories by Philip Jenkins. When I’ve “taught” church history or creeds and confessions in our church, my denominational diagram shows as its first split the one between Rome and Constantinople–the idea being that Arianism and other Trinitarian and Christological errors were severe enough to exclude from the definition of orthodox. I’ve wondered at times if I should put the Oriental Church back on the orthodox branch but with a split earlier than 1100.

  6. One can best understand the hypostatic union (together united in one subsistence and in one single person) by examining what it is not, thus from the process of elimination determine what it must be.

    It is not:

    1. a denial that Christ was truly God (Ebionites, Elkasites, Arians);
    2. a dissimilar or different substance (anomoios) with the Father (semi-Arianism);
    3. a denial that Christ had a genuine human soul (Apollinarians);
    4. a denial of a distinct person in the Trinity (Dynamic Monarchianism);
    5. God acting merely in the forms of the Son and Spirit (Modalistic Monarchianism/Sabellianism/United Pentecostal Church);
    6. a mixture or change when the two natures were united (Eutychianism/Monophysitism);
    7. two distinct persons (Nestorianism);
    8. a denial of the true humanity of Christ (docetism);
    9. a view that God the Son laid aside all or some of His divine attributes (kenoticism);
    10. a view that there was a communication of the attributes between the divine and human natures (Lutheranism, with respect to the Lord’s Supper); and
    11. a view that Jesus existed independently as a human before God entered His body (Adoptionism).


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