If it looks like a duck, walks like a duck, and quacks like a duck, it’s a duck. Surely you have heard the old saying. That may be true when describing the state of duckness—the essence of what it means to be a duck—but when we talk about God and the things of God, does the same hold up? I am assuredly not comparing God to a duck but merely being mindful of the fact that, when essential qualities are shared, we see an equality. There is equality in the essence of the persons of the Trinity.

The true church understands this essential equality. But the church has had to grapple throughout history as she contended for truth. From the Monarchians to the Socinians to the Unitarians, there have been those who reject the equality of the three persons of the Trinity.

Question 11 of the Westminster Larger Catechism reminds us that the Son and Holy Spirit are “God equal with the Father.” The four categories that serve as testimony of this assertion, categories that the Father, Son, and Spirit share, are names, attributes, works, and worship.

Through the proof texts, the catechism calls on you to open your Bible and to study the Word. Isai-ah 6 is the quintessential chapter on the holiness of God. We see the name Lord and Lord. The titles “Lord of hosts” and “king” are used. We see something of the diversity of persons with the use of the word “us.” And we see the attributes of “holiness” and “eternality.” The work of sanctification is happening in the text. We see seraphim worshiping the one on the throne. Clearly this is God. The catechism then takes the reader to John 12 where, following “many signs,” the apostle quotes from Isaiah 6 and concludes in verse 41, “These things Isaiah said when he saw His glory and spoke of Him.”

Amazing, right? Jesus is in Isaiah 6! According to John, Isaiah spoke of Jesus through the names of God, attributes of God, works of God, and worship of God.

A fascinating trail of proof texts is presented to help us see that both the Son and the Holy Spirit share names, attributes, works, and worship. Another example given is in Acts 5 when Ananias and Sapphira chose to lie about the sale price of a property to inflate how generous they were be-ing. In verse 3, Peter accused of them of “lying to the Holy Spirit,” and in verse 4, he said that they had “not lied to men but to God.”

Grasping the proposition of equality that the catechism puts forth and studying the logic of the proof texts, the reader does see that “the Son and the Holy Ghost are God equal with the Father” just as proposed. J. G. Vos concludes, “The only conclusion that can logically be drawn from the biblical data is that there is only one God, who exists in three distinct persons each of which is truly God and equal with the other two” (Vos’s Commentary on the Larger Catechism).

The truthfulness of unity and diversity within the Godhead, the persons of the Trinity being distinct while sharing an essence, and other deep truths of the mystery called the Holy Trinity may not be fully grasped in this life—but we can grasp something of it. Question 11 gives us the duck test that shows that the Father, Son, and Holy Spirit all share names, attributes, works, and worship.

The 17th Century Covenanter, Hugh Binning, while meditating on this catechism question, helpfully concluded, “It is a great mystery to keep the right middle way. Learn…so to conceive of God, and so to acknowledge him, and pray to him, as you may do it in the name of Jesus Christ, that all the persons may have equal honor, and all of them one honor; that while you consider one God, you may adore that sacred and blessed Trinity; and while you worship that Holy Trinity, you may be straightway reduced to an unity. To this wonderful and holy One, Father, Son, and Holy Ghost, be all praise and glory” (Hugh Binning, Common Principles of the Christian Religion, 1.154).

When, as in Question 11, we consider the Trinity, the conclusion is worship, adoration, and praise. Meditate here and give God—Father, Son, and Holy Spirit—the glory due His holy name.