Radisson finds the topic of religion painful because his Christian mother died when he was 12, though he had prayed and begged God to spare her life. This may be what led him to study philosophy so in-depth that he ultimately became a philosophy professor, but his desire to now avoid the topic of religion does not mesh well with his career as a philosophy professor. His anger at God has him requesting his students quote Friedrich Nietzsche and, in exchange, he promises to allow them to skip the chapter on religion. This is not the only clue the movie makers give that they have read atheist material extensively. Radisson tells Josh that if he won't reach a consensus with the class, he must prove God is not dead. Radisson had already explained this was a metaphor and, taken in the context of Nietzsche's point, Josh does an excellent job of proving this. Radisson promises Josh that he will keep his comments to a minimum (Radisson won't debate Josh), though Josh begins his argument practically begging for the most common atheist argument when he says "I say you can't prove God does not exist". Radisson promised he would not debate Josh, and he keeps this promise. We are given more clues as to why when we discover Radisson married a Christian and his hostility towards God roots from his love for his Christian mother.