The printing metaphor was not chosen because it looks good. The number four, and the way four elements combine into one whole, recurs wherever wholeness is possible at all: in full-colour printing, in the structure of DNA, and in Scripture itself. This does not prove the Gospel — it shows that the principle of fullness through complementarity is not confined to theology.
DNA has four letters, but they do not combine at will. A large base always stands opposite a small one: A with T, G with C. Only then does the helix keep a constant width and the structure hold. The four witnesses to Jesus join the same way — opposite to opposite.
A large base never bonds to another large one, only to a small one. Majesty is not held up by more majesty but by abasement: the King takes the servant's place, and that is what makes the authority stable. Remove either side and the bond breaks: authority without service becomes domination, service without authority loses its ground.
The second pair holds by three bonds instead of two — the strongest link in the helix. So here: the union of the divine and human natures in one Person is not the weak point of the doctrine but its strongest. It is what holds everything else, and it is the first thing anyone tries to break.
Different, yet complementary, forming a single whole. The helix holds not because the elements are alike, but because each is bonded to its opposite.
This is not a convention but a property of ink. Cyan, magenta and yellow give colour but not depth: their overlap never reaches a true black, edges go soft, detail is lost. The fourth form colours nothing — it gives definition.
Metallic gold cannot be produced by mixing CMYK: however carefully you set the percentages, you get a brown-yellow, never a shine. It is printed as a separate form — a spot colour. So Acts is not a fifth Gospel either: it is what cannot be derived from the four, and without which the impression stays dead.
The question “why four Gospels, not one and not twenty” is not new. It was answered in the second century, and answered in terms of fullness rather than compromise.
Four faces around the throne: lion, ox, man, eagle. From early times they were matched with the four evangelists: the royal, the serving, the human and the heavenly in one vision.
Ezekiel 1:10 · Revelation 4:7He argued directly against those who wanted to cut the witness down to one Gospel or add their own: four is neither accident nor oversight but the necessary fullness of the witness to Christ.
Against Heresies III.11.8Four winds, four corners of the earth, four directions. The Gospel does not come to one corner of the world but to all four — and so the witness to it is likewise fourfold.
Isaiah 11:12 · Matthew 24:31Acts does not extend the series of four. It shows what comes after: the ascension, the outpouring of the Spirit, and the Church as witness. A separate form, not a fifth shade.
Acts 1:8 · 2:1–18