29. Another analogy which casts some light upon the meaning of the faith is that of fire as containing fire in itself and as abiding in fire. Fire contains the brightness of light, the heat which is its essential nature, the property of destroying by combustion the flickering inconstancy of flame. Yet all the while it is fire, and in all these manifestations there is but one nature. Its weakness is that it is dependent for its existence upon inflammable matter, and that it perishes with the matter on which it has lived. A comparison with fire gives us, in some measure, an insight into the incomparable nature of God; it helps us to believe in the properties of God that we find them, to a certain extent, present in an earthly element. I ask, then, whether in fire derived from fire there is any division or separation. When one flame is kindled from another, is the original nature cut off from the derived, so as not to abide in it? Does it not rather follow on, and dwell in the second flame by a kind of increase, as it were by birth? For no portion has been cut off from the nature of the first flame, and yet there is light from light. Does not the first flame live on in the second, which owes its existence, though not by division, to the first? Does not the second still dwell in the first, from which it was not cut off; from which it went forth, retaining its unity with the substance to which its nature belongs? Are not the two one, when it is physically impossible to derive light from light by division, and logically impossible to distinguish between them in nature.