Logical Debate
Seeing as Hume is following the format laid out in Plato's philosophical writings, he frames his arguments by a logical debate between three philosophers, with a young witness playing the role of Plato observing his master, Socrates. The debate, while not following the traditional order of a formal debate, adheres to reason and logic. Each of the participants is willing to change his opinion if presented a convincing, cohesive argument. They take turns asserting and criticizing points. While some of the participants seem more motivated to be correct than others, they all agree to use the standard of logical arguments in order to arrive at a conclusion. The end of the debate is inconclusive, however. Neither of the three has been persuaded to change their perspective, although Pamphilus seems to think his master, Cleanthes is the real victor. This conclusion in and of itself is probably an instance of bias.
The Power of the Human Mind
Since the book revolves around open argument, it necessarily addresses the means by which argument is presented -- the mind. Each of the philosophers wrestles with their own inability to adhere to absolute truth. Since they are human, they are subject to bias, if only from misinformation and ignorance. Nonetheless, they all acknowledge the somewhat futile nature of their arguments. Without God himself answering their questions, however, debate is the only method by which logical conclusions can be achieved. Philo focuses on this weakness of the mind in his argument for the mysteriousness of the nature of God.
Suffering
One of the main debates in which the philosophers engage in the text is that of the nature of God as evidenced by suffering. They argue about the balance of suffering and pleasure in life, whether one outweighs the other. If the balance is imperfect, then what would that mean for the divinity and authority of God? Additionally the argue about the attribution of suffering to God. If God is the origin of suffering as well as goodness, then He would be ultimately powerful. What's the appropriate response to a being which has produced both suffering and goodness? Demea believes in faith above all else. In his opinion, disloyalty to God is the ultimate sin, even for the sake of reason. Both Cleanthes and Philo, however, disparage his opinion because they are preferring logic to emotion. They believe that a God who has ordered the natural universe has also established logic as a framework through which He may be understood.
