Question: "What is dualism?"
Answer: In theology, the concept of dualism assumes that there are two separate and equal entities— good and evil—which are equally powerful. God represents the good entity and Satan represents the evil entity.
However, the problem here is that, even though Satan has some power, he is no equal to God Almighty, for he was created by God in the form of an angel before he fell from heaven because of his rebellion (Isaiah 14:12-15; Ezekiel 28:13-17). As the Scripture says, "Ye are of God, little children, and have overcome them; because greater is He that is in you than he that is in the world" (1 John 4:4, KJV). So, according to Scripture, there is no dualism, no two opposing forces of equal power called Good and Evil. Good, represented by God Almighty, is the most powerful force in the universe without exception. Evil, represented by Satan, is a lesser force that is no match for Good. Evil will be defeated every time in any head-to-head match with Good, for God Almighty, the essence of Good, is all powerful whereas Evil, represented by Satan is not all powerful.
Whenever any doctrine portrays Good and Evil as two equal opposing forces, that doctrine contradicts the scriptural position that Good, represented by God Almighty, is the dominant power in the universe. Since Satan was not, and never will be, equal to God, any doctrine that says he is can be marked as a false doctrine. Just because Satan was thrown out of heaven for trying to rise above God and be worshipped in His stead, does not mean that Satan has given up trying to be equal or superior to God, as is evidenced by the basic tenets of "dualism" that have come down largely through the philosophical stem of human wisdom.
There can be no dualism existing in any corner of our universe, irrespective of what our philosophers tell us. There is only one power that is the overriding power over everything, and that power is God Almighty as He is revealed to us in the Bible. Hence, according to the scriptural evidence, there is only one power that is omnipotent, not two. Thus, any doctrine of dualism which contends that there are two equal powers opposing each other (good and evil) is a false doctrine.