The Rainbow as an Image of the Trinity

“Look upon the rainbow, and bless him that made it: it is very beautiful in its brightness. It encompasseth the heaven about with the circle of its glory, the hands of the most High have displayed it.” (Sir. 43)

(From St. Basil the Great’s Thirty-Eighth Letter, to his brother Gregory.)

You have before now, in springtime, beheld the brightness of the bow in the cloud; the bow, I mean, which, in our common parlance, is called Iris, and is said by persons skilled in such matters to be formed when a certain moisture is mingled with the air, and the force of the winds expresses what is dense and moist in the vapour, after it has become cloudy, into rain.

“Your signs bring deliverance, to me Your cross and to Noah Your bow!” (St. Ephrem)

The bow is said to be formed as follows. When the sunbeam, after traversing obliquely the dense and darkened portion of the cloud-formation, has directly cast its own orb on some cloud, the radiance is then reflected back from what is moist and shining, and the result is a bending and return, as it were, of the light upon itself. For flame-like flashings are so constituted that if they fall on any smooth surface they are refracted on themselves; and the shape of the sun, which by means of the beam is formed on the moist and smooth part of the air, is round. The necessary consequence therefore is that the air adjacent to the cloud is marked out by means of the radiant brilliance in conformity with the shape of the sun’s disc.

“The rainbow is called a bow from what the Lord spoke to Noah and to his sons, that they should not fear any further deluge in the generation of God, but fire.” (St. Victorinus)

Now this brilliance is both continuous and divided. It is of many colours; it is of many forms; it is insensibly steeped in the variegated bright tints of its dye; imperceptibly abstracting from our vision the combination of many coloured things, with the result that no space, mixing or paring within itself the difference of colour, can be discerned either between blue and flame-coloured, or between flame-coloured and red, or between red and amber. For all the rays, seen at the same time, are far shining, and while they give no signs of their mutual combination, are incapable of being tested, so that it is impossible to discover the limits of the flame-coloured or of the emerald portion of the light, and at what point each originates before it appears as it does in glory.

“As the appearance of the rainbow when it is in a cloud on a rainy day: this was the appearance of the brightness round about.” (Ezekiel 1)

As then in the token we clearly distinguish the difference of the colours, and yet it is impossible for us to apprehend by our senses any interval between them; so in like manner conclude, I pray you, that you may reason concerning the divine dogmas; that the peculiar properties of the hypostases, like colours seen in the Iris, flash their brightness on each of the Persons Whom we believe to exist in the Holy Trinity; but that of the proper nature no difference can be conceived as existing between one and the other, the peculiar characteristics shining, in community of essence, upon each.

“And he that sat, was to the sight like the jasper and the sardine stone; and there was a rainbow round about the throne, in sight like unto an emerald.” (Apoc. 4)

Even in our example, the essence emitting the many-coloured radiance, and refracted by the sunbeam, was one essence; it is the colour of the phænomenon which is multiform. My argument thus teaches us, even by the aid of the visible creation, not to feel distressed at points of doctrine whenever we meet with questions difficult of solution, and when at the thought of accepting what is proposed to us, our brains begin to reel.

(Source: New Advent, trans. Blomfield Jackson)