5.  Yet receive what I say as at best a token and reflexion of the truth; not as the actual truth itself.  For it is not possible that there should be complete correspondence between what is seen in the tokens and the objects in reference to which the use of tokens is adopted.  Why then do I say that an analogy of the separate and the conjoined is found in objects perceptible to the senses?  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.  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.  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 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.  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.  In regard to visible objects experience appears better than theories of causation, and so in matters transcending all knowledge, the apprehension of argument is inferior to the faith which teaches us at once the distinction in hypostasis and the conjunction in essence.  Since then our discussion has included both what is common and what is distinctive in the Holy Trinity, the common is to be understood as referring to the essence; the hypostasis on the other hand is the several distinctive sign. The scientific part of the analogy of the rainbow is of course obsolete and valueless.  The general principle holds good that what is beyond comprehension in theology finds its parallel in what is beyond comprehension in the visible world.  We are not to be staggered and turn dizzy in either sphere of thought at the discovery that we have reached a limit beyond which thought cannot go.  We may live in a finite world, though infinite space is beyond our powers of thought:  we may trust in God revealed in the Trinity, though we cannot analyse or define Him.