In contemplation of the many theologies of Christianity, one prevalent tension lies in the paradox of how evil may exist in light of a good God, namely the study of theodicy. This complex issue may misguide believers and critics alike if not thoroughly analyzed. Thomas Aquinas as well as Augustine address this issue in addition to those of free will in light of the existence of good and evil as well as suffering.
In the view of Christian theism, God is immutable. In relation to evil, it is addressed how God may cause and/or allow evil to exist. It is understood a pre-eminent mover must put everything into effect. It is then concluded God permits evil to exist but He does not set it into motion. Augustine states merely the absence of good defines evil. So where evil exists, good does not. Also in light of Augustine it is pivotal to address his statement, “ The incorruptible is superior to the corruptible.” In dealings of the paradox of good and evil there must be an understanding of the soul, which could change for the worse through free choice or could be corrupted by sin. It is neither a part of God nor of the same nature as God, but is created by Him, and is far inferior to its Creator.
In regards to free will in light of the tension of good and evil, Thomas Aquinas addresses the issue elegantly. First the actuality of free will is to be addressed. It may be argued that man has no free will at all, but Aquinas points out that if free will were not in existence, exhortations, commands, prohibitions, rewards and punishment would be in vain. As humans we are created as rational beings; in order to be rational we must have free will. In light of salvation, free will is still in existence but not in total effect unless moved and assisted by God. Romans 9:16 states, “So then it depends not on human will or exertion, but on God, who has mercy.” We see that man has some choice in what he does; therefore, there must be a persistent alternative to God and all that is good for man to truly make a choice to follow. So it may be concluded that man has free will and to choose God it must be moved. By allowing this free will— this choice— God subsequently had to allow evil to enter the world.
In reference to evil, there are many subcategories of wrong. The two most basic are those that are caused by natural processes and actions of humans. Earthquakes, hurricanes and other weather related disasters do not result from morally wrong actions, but exist, kill, wound and harm humanity. Whereas free will is a plausible argument for an explanation of human evils it does not directly account for natural evil. The best explanation of natural evil may be traced back to the fall. All processes and attributes of the universe were in perfection, and in the fall all were perverted in some way. Generally evil is found as necessary because it is the optimal way for God to display His love to His creation. This is true because the world was foundationally formed to display the glory of God in physical form; likewise, all occurrences within it exhibit the glory of God.
Aside from evil in and of itself also there presides the problem of the effects of things evil, namely suffering. William Lane Craig aims to tackle the issues of suffering and evil and explains it as such: “God may permit suffering in our lives to build us or test us, or to build and test others, or to achieve some other overriding end.” In assessing suffering and attempting to pin down a definite cause we begin to put limits on God as to why we are suffering as we are. Romans 8:28 states that all things work together for the good for those that love the Lord and in 1 Peter 4:12 we are told not to be surprised at the ordeal we are suffering, but to know in those sufferings that they produce perseverance and ultimately brings glory to God.
Yet, still to be expounded upon is how God permits evil in human actions. It is understood man has a choice in choosing to act morally, in choosing good or immorally choosing evil. It is possible to state that God may value free will enough to allow humans to commit horrendous acts rather than to prevent them and take away their allowance of free will. Most mainstream Christians believe that in an instance such as this that God will have His justice in the end and punish those who have done evil and show mercy and compassion upon those who have been victimized by evil. This philosophy accepts that God allows evil and free will and although all may not comprehend the evils that occur, one may rest in knowing there will be justice for all in the end.
It is resulted that evil may exist in light of a good God, and that He may use evil as well as good to work together ultimately to the glory of His Name. It is often lost sight of that all that is, has been and will be works together to the chief end of His glory. Because of various utilities such as councils and commands in addition to rewards it may be understood man has free will. In light of free will man is able to choose between good and evil. God allows evil to exist, and it has existed due to the fact evil in and of it itself is merely the absence of good.

“The greatest gift that God in His bounty made in creation, and the most conformable to His goodness, and that which He prizes the most, was the freedom of will, with which the creatures with intelligence, they all and they alone, were and are endowed.”
~ Dante Alighieri (1265-1321)