763. The reason why it is a principle of order that what is first should advance, both generally and in detail, to its last state, is to permit everything to be varied; and it is varieties which determine quality, for quality is perfected by differences relating to what is more or less its opposite. Can anyone fail to see that truth gets its quality from the existence of falsity; and likewise good gets its quality from the existence of evil, light its from the existence of darkness, heat its from the existence of cold? How could we have colour, if only white existed and no black? It is only incompleteness which produces the quality of the intervening colours. How could we have meaning without contrast, and contrast except by reference to opposites? Is not the eyesight dimmed by nothing but white, and enlivened by colour; and colour owes something to black, as for instance, green does. Does not the ear go deaf, if a single note is continually dinned into its organs? But it is aroused by variation of pitch, and this too is the result of contrasts. How can we have beauty without a contrast with ugliness? That is why the beauty of some young woman is vividly displayed in some paintings, which have an ugly face put alongside. How could we have pleasure and bliss, except by contrast with what is unpleasant or unblest? Does not a single idea held constantly in the mind drive one mad, unless it is varied at intervals by ideas tending in the opposite direction?

It is much the same with the spiritual things of the church; here the opposites refer to evil and falsity. Yet these do not come from the Lord, but from human beings, who have free will and can apply it to good or to evil purposes. To use a comparison, it is the same as with darkness and cold. These do not come from the sun, but from the earth, which as it revolves successively withdraws from and turns away from the sun. Yet were it not for this turning towards and withdrawal, there would be neither days nor years, and so nothing, indeed, no one, upon earth. I have been told that churches which possess differing kinds of good and truth, so long as the kinds of good they have relate to love to the Lord and the truths they have relate to faith in the Lord, are like so many jewels in a king's crown.