Quote 1
It was on the moral side, and in my own person, that I learned to recognise the thorough and primitive duality of man; I saw that, of the two natures that contended in the field of my consciousness, even if I could rightly be said to be either, it was only because I was radically both; and from an early date, even before the course of my scientific discoveries had begun to suggest the most naked possibility of such a miracle, I had learned to dwell with pleasure, as a beloved daydream, on the thought of the separation of these elements. If each, I told myself, could be housed in separate identities, life would be relieved of all that was unbearable; the unjust might go his way, delivered from the aspirations and remorse of his more upright twin; and the just could walk steadfastly and securely on his upward path, doing the good things in which he found his pleasure, and no longer exposed to disgrace and penitence by the hands of this extraneous evil. It was the curse of mankind that these incongruous faggots were thus bound together—that in the agonised womb of consciousness, these polar twins should continuously be struggling. How, then, were they dissociated? (10.1)
Dr. Jekyll believes that good and evil should be separated from each other because he can not balance them well when they are mingled.
Quote 2
Both sides of me were in dead earnest; I was no more myself when I laid aside restraint and plunged in shame, than when I laboured, in the eye of day, at the futherance of knowledge or the relief of sorrow and suffering. (10.1)
Good and evil exist in equal parts in Dr. Jekyll.
Quote 3
Enough then, that I not only recognised my natural body from the mere aura and effulgence of certain of the powers that made up my spirit, but managed to compound a drug by which these powers should be dethroned from their supremacy, and a second form and countenance substituted, none the less natural to me because they were the expression, and bore the stamp of lower elements in my soul. (10.2)
Interestingly, Dr. Jekyll’s potion results in pure evil, rather than pure good.