In the philosophy of religion, it is often asked what it means for God to be perfect and perfectly good. 

This question is pertinent to ‘perfect being theology’. Here it is thought that being perfect, including perfectly good, is essential to what “God” is. God being a perfect Being entails that he is perfectly good, which is what traditional theistic religions typically affirm: God is a perfect Being who is perfectly good.

Can God be less than perfect and perfectly good? Many would argue not. God being less than a perfect Being who is perfectly good means that we could think of a Being superior to God, namely a Being who is perfect and a perfectly good. This being would therefore be God.

God being perfect and perfectly good is linked to the notion of God deserving unconditional gratitude, praise, and worship. To be less than perfectly good would make God unworthy of unreserved praise and worship. Since perfect goodness is a part of a perfect God’s nature, God cannot fail or cease to be perfectly good. For instance, God cannot do what is morally wrong because that is inconsistent with his perfect goodness. It is no more logically possible for a perfect God to be immoral than it is possible for there to exist a four-sided triangle.  

Part of being perfectly good is to be morally perfect. Many theists believe God is the source of moral duties. This includes both negative duties (e.g. the duty not to take innocent human life) and positive duties (e.g. the duty to help others in need). Many religious people think duties are grounded in divine commandments. For example, a Jewish person might view the Ten Commandments as fundamental moral rules that determine what he is morally obligated to do or refrain from doing. 

Many religious people justify God’s perfect goodness from their sacred texts. Christians appeal to Jesus who taught that “No one is good except God alone” (Luke 18:19) and to the Psalmist who wrote that “the Lord is good and his love endures forever” (100:5). Because God is perfectly good, he is loving and faithful, and since God is perfectly good, he always desires to do good.

God’s perfect nature and perfect goodness are challenged by the ‘argument from evil’. The argument posits that because the world contains evil, the world is not under the control of an absolutely perfect Being, especially not a God who is omniscient, omnipotent, and morally perfect. The problem of evil continues to be a hot topic of debate in the philosophy of religion and between theists and their intellectual counterparts.