A theodicy is an attempt to defend God's goodness in view of the existence of evil. They are common to monotheistic religions based on the Abrahamic tradition, namely Judaism, Christianity, and Islam, as these all suffer from the problem of evil.
In short, the problem of evil occurs when specific attributes are ascribed to God:
- Omniscience (all-knowing)
- Omnipotence (all-powerful)
- Omnibenevolence (infinite goodness)
Given these three attributes, God should know evil things will happen, have the power to prevent them, and the desire and will to prevent them. Since evil things happen nonetheless, it must be assumed that god lacks one of these three attributes.
A theodicy attempts to explain how God can retain these attributes despite the existence of evil.
Theodicy is not found in all theistic beliefs, as not all theistic traditions ascribe the same attributes to God. Some polytheistic religions, for example, do not ascribe any god the quality of omnipotence. If a god does not have the power to prevent evil, then the dilemma is avoided in his case.
Looking at the bible we can ascertain that God is not Omniscient (all-knowing). This misconception of God being all-knowing, comes from the fact that there are prophecies in the bible. However in Jewish thought prophecy was not "for-speaking" but "forth-speaking." It is the idea that God is declaring to the prophets something he will do in the future. Prophecies do not substantiate the claim that God has foreknowledge. Being far wiser than us, he may be able to predict what may happen (just like a supercomputer does today) but it is never cut into stone.
St. Augustine's Theodicy: Blame it on the Fall from Eden
St. Irenaeus's Theodicy: Evil serves a purpose.