Does the Coptic Church believe in a Dualistic view of the world where God is a completely separate entity from the devil, or does the Church support the monotheistic theory that God created evil? If so, then is God the direct source of evil, or is there some other explanation for evil through a monotheistic belief?
God did not create evil. Evil is lack of goodness. God made Satan as the most beautiful of all creatures (Ezek 28:14-15). Satan, by his own free will, rebelled against God "Your heart was lifted up because of your beauty; you corrupted your wisdom for the sake of your splendor" (Ezek 28:17) and wanted to be like the Most High (Is 14:12-15). Similarly, when we sin, ultimately we (by our free will) are the cause of the evil we do.
When Saul had forsaken God and his duty, God, in a way of righteous judgment, withdrew from him the assistance of the good Spirit with which he had been directed. When the Spirit of the Lord departs from us, we lose everything.
When men grieve and quench the Spirit, by willful sin, He departs. With Saul, the consequence of this was that an evil spirit from God troubled him. Those that drive the good Spirit away become prey to the evil spirit. If God and His grace do not rule us, sin and Satan by divine permission, will have access in our lives.
"I form the light and create darkness, I bring prosperity and create disaster; I, the Lord, do all these things" (Isaiah 45:7). Now, as darkness is only the privation of light, so disaster is the privation of prosperity and the evil of war is the privation of peace.
God here wants to assert His omnipotence and absolute supremacy. "I am the LORD, and there is no other; There is no God besides Me." (Isa 45:5) Because at the time of Isaiah, the great principle of the Magian religion, prevailed in Persia in the time of Cyrus. This principle taught that there were two supremes, co-eternal, and independent causes always acting in opposition one to the other; one the author of all good, the other of all evil. They called the good being LIGHT; and the evil being, DARKNESS. Thus when LIGHT had the ascendant, then good and happiness prevailed among men; when DARKNESS had the superiority, then evil and misery abounded. This opinion contradicts the clearest evidence of our reason, which plainly leads us to the acknowledgment of one only Supreme God, infinitely good as well as powerful.