Answer
The prefixes di- and bi- both relate to the number two. Sometimes these terms are used interchangeably to describe systems that acknowledge two (primary) deities. At times, these deities are viewed as two principles rather than personal gods. Both bi- and ditheism represent forms of dualism, and occasionally bitheism or ditheism are known by these names. It is important to recognize that there are also types of dualism that do not involve any gods. Some atheists are dualists who believe in a dualism of mind-body or matter-energy without any deities.
When distinguishing between bitheism and ditheism, ditheism typically denotes a type of dualism that asserts the equality and opposition of the two primary deities, one being good and the other evil.
Bitheism acknowledges two deities that are not in conflict but rather complementary. For instance, in Hinduism, Shiva and Vishnu have contrasting roles but are not hostile towards each other. Both Vishnu and Shiva originate from the supreme god Brahma, the creator, whose task is now complete. Vishnu sustains the universe, while Shiva is the destroyer. However, these roles are viewed as complementary in effecting change. They are not adversaries; in some texts, they are even depicted as worshipping and aiding each other as needed. (Shiva and Vishnu are Hinduism’s primary deities, although Hinduism is rightly classified as polytheistic, not bitheistic, due to its numerous gods.)
It is crucial to remember that the Bible does not espouse bitheism or ditheism. Some individuals mistakenly perceive God and Satan as two equal, opposing forces, with humans sometimes seen as the deciding factor in the conflict. The Bible teaches that God is the Creator of all and has no equals. He is the Only God. “This is what the Lord says—Israel’s King and Redeemer, the Lord Almighty: I am the first and I am the last; apart from me there is no God. Who then is like me? . . . You are my witnesses. Is there any God besides me? No, there is no other Rock; I know not one” (Isaiah 44:6-8).
Satan is certainly opposed to God, but he lives under God’s authority. Satan cannot do anything without God’s oversight. For example, when Satan wanted to persecute Job, he had to gain God’s permission first. (See Job 1—2.) Satan’s freedom is limited in scope and duration. In the final judgment, he will be cast into the lake of fire «And the devil that deceived them was cast into the lake of fire and brimstone, where the beast and the false prophet are, and shall be tormented day and night for ever and ever. », (Revelation 20:10). For a time Satan opposes God, but ultimately, even Satan’s opposition and rebellion are part of God’s plan and will result in His glory.