This article is a study of how Augustine's ethics of belief shaped his arguments against unbelief and its legacy in using coercion to settle disputes. After considering the arguments for belief presented by Augustine, the article studies how these were shaped by his understanding of the problem of evil and how the Fall influenced free will. What is noted to be of benefit in Augustine is that he offers arguments in favor of belief, and is convinced that he has shown unbelief to be based on unsound reasoning. By way of contrast, a number of theologians (such as Tertullian, John Calvin, and those under the heading of Reformed Epistemology) are considered who do not believe that arguments are necessary to support belief or reject unbelief. These are contrasted with Augustine and it is argued that they have significant shortcomings in this respect. However, the article concludes that Augustine could have gone farther in supporting the claim that it is clear that God exists, and his own shortcomings have been used to justify coercion in religious belief. If common ground is to be achieved this problem must be corrected and an adequate foundation for clarity must be established.