Dionysius here touches incidentally on a mystical doctrine which, as developed by later writers, afterwards attained the greatest importance. This doctrine of a timeless self is the postulate, perhaps, of all Christian mysticism. The boldest expression of it is to be found in Eckhart and his disciple Tauler, who both say that even the lost souls in hell retain unaltered the ultimate nobility of their being. And lest this doctrine should be thought to trifle with grave matters, be it remembered that the sinfulness and gravity of sin are simply due to this indestructible nobility of our being. Man cannot become non-moral, and hence his capacity for wickedness. The soul is potentially divine, and therefore may be actually satanic. The very devils in hell cannot destroy the image of the Godhead within them, and it is this image that sin defiles.
It follows from the ultimate non-entity of evil that, in so far as it exists, it can only do so through being mingled with some element of good. To take an illustration given by Dionysius himself, where there is disease there is vitality, for when life ceases the sickness disappears in death. The ugliness of evil lies precisely in the fact that it always, somehow or other, consists in the corruption of something inherently good.
It is, however, this ugliness of things that Dionysius fails to emphasize, and herein lies the great weakness of his teaching. Not only does he, with the misguided zeal of an apologist, gloze deliberately over certain particular cruelties of the Creation and accept them as finite forms of good, but also he tends to explain away the very nature of evil in itself. He tends to be misled by his own true theories. For it is true that evil is ultimately non-existent. St. Augustine taught this when he said: "Sin is nought";  so did Julian of Norwich, who "saw not sin," because she believes "it hath no manner of substance nor any part of being."  The fault of Dionysius is the natural failure of his mental type to grasp the mere facts of the actual world as mere facts. He is so dazzled with his vision of ultimate Reality that he does not feel with any intensity the partial realities of this finite universe. Hence, though his theory of evil is, in the main, true, he does not quite grasp the true application of his theory to this world of actual facts.
For this world is by its very nature finite. And hence, if the evil in it is (as Dionysius rightly says) but partial, it must also be remembered (as he for a moment forgets) that its very existence is but partial. And, therefore, though evil is ultimately non-existent, yet the bad qualities of things may, so far as this present world is concerned, have as much reality, or at least as much actuality, as their good qualities. And when we say that evil is ultimately non-existent we merely mean that evil ought to have no actuality here, not that it has none. Dionysius calls evil a lapse and failure of the creature's proper virtues. But a lapse or failure has in it something positive, as he in the same breath both admits by using the word and also tries to explain away. It is as positive as the virtues from which it lapses. The absence of a wooden block is nothing, light has no proper place there, but the air, where light should is darkness and is a visible shadow. St. Augustine has crystallized this truth in his famous epigram, quoted above in part, which runs in full as follows: "Sin is naught, and men are naughtes when they sin." The void left by the want of a good thing has a content consisting in the want. Probably had Dionysius seen more of the world's misery and sin he would have had a stronger sense of this fact. And in that case he mould have given more prominence than he gives, in his extant writings at least, to the Cross of Christ.
Two things should, however, be borne in mind. In the first place he is writing for intellectual Christians in whom he can take for granted both an understanding of metaphysics and a horror of sin. To such readers the non-existence of evil could not have the same meaning as it would to the world outside. For the same reason he (like other Christian teachers after him) speaks of God's transcendent Non-Existence without fearing lest his words should be interpreted as atheism. In fact, to guard against misinterpretation he utters the express warning that mysteries can only be taught to the Initiated. 
In the second place throughout his whole treatment of evil, he is no doubt writing with an eye on the dualistic heresy of the Manichees, which was prevalent in his day. Hence the occasional indiscretion of the zeal with which he seeks to block every loop-hole looking towards dualism. The result is a one-sided emphasis in his teaching rather than positive error. He rightly denies a dualism of ultimate realities; but he tends to ignore, rather than to deny, the obvious dualism of actual facts.
Before proceeding to the Method of Contemplation which crowns and vitalizes the entire speculative system of Dionysius, it will be well to bring together in one paragraph the various meanings he gives to Non-Existence.
(1) The Super-Essence transcends the distinction between the Aristotelian "Matter" and "Form"; but in this world the two are distinct from each other. And whereas, in this world, Form without "Matter" has an abstract existence for thought, "Matter" with out Form has none. Thus mere "Matter" is non-existent. And hence things both before their creation and after their destruction are non-existent, for their "Matter" has then no "form." (2) Similarly Good without evil exists as the highest Manifestation or "Form" of the Godhead, but evil without Good is formless and therefore non-existent. (This does not mean that "Matter" or the world-stuff is evil, but that neither it nor evil is anything at all.) And since evil is ultimately altogether non-existent, all things are non-existent in so far as they are evil. (3) Finally, the Super-Essence is, in a transcendent manner, non-Existent as being beyond Existence. And hence the paradox that the destructive force of evil and the higher impulse towards the Godhead both have the same negative principle of a discontent with the existent world -- the dangerous, yet true, doctrine (taught, among others, by St. Augustine  and Dante  ) that evil is a mistaken quest for Good.
The principle of this classification is quite simple. It lies in the fact that Being is the most universal of the Emanations or Forms, and that all things therefore exist only in so far as they possess Form. Hence the want of all "form" is non-entity and makes things which are without any form to be non-existent; that want of proper "form" which we call evil is a tendency to non-entity and makes evil things to be so far non-existent; the want of complete substantial or spiritual "form" makes merely existent things (i.e. lifeless things) to be "un-existent"; and the transcendence of all "Form" makes the Super-Essence to be in a special sense "Non-Existent."
The theory of evil, as given above, is worked out in a manner sufficiently startling.
We naturally divide existent things into good and bad and do not think of non-existent things as being things at all. Dionysius, with apparent perversity, says all things are good, and then proceeds to divide them into "Existent" and "Non-Existent"! The reason is this: All things have two sides to their being: the one in the Super-Essence and the other in themselves. In the Super-Essence they are eternally good, even before their creation. But in themselves (i.e. in their created essence) they were wholly non-existent before their temporal creation, and after it are partially non-existent in so far as they are tainted with evil.
 Com. on St. John 1:13. Cf. Conf. vii. 18; xii. 11.  Revelations of Divine Love, xxvii.  Div. Nom. i. 8, ad fin.; Myst. Theol. i. 2.  Conf. ii. 6, 12-14  Parad. v. 10-12
 Revelations of Divine Love, xxvii.
 Div. Nom. i. 8, ad fin.; Myst. Theol. i. 2.
 Conf. ii. 6, 12-14
 Parad. v. 10-12