The difficulty of logic
Logic is a beautiful and obvious aspect of nature, and although they do not agree on much, the philosophers agree on that. However, just because there are aspects of reason that seem elementary and obvious, the actual practice of constructing a true argument of any serious worth is actually ironically difficult. This is because so much of reality is taken for granted, and in order to be exactly true and precise in one's argument, one has to step out of reality taken for granted. That step out of taking things for granted is a step into absolute skepticism for Philo (and Hume himself). From the absurdity of skepticism, a sufficient logical proof becomes incredibly rare indeed.
The ease of deconstruction
Compared to constructing a logical argument, it is fairly easy to prove something as untrue. This is because, as Philo repeats over and over again, a person does not have to prove an argument false; they have to prove it not necessarily true. By exposing any logical shortcuts or missing third terms in any syllogism, a person can very quickly deduce that an argument is not sufficiently forceful. The ease of deconstruction is a helpful tool, because if there is anything easier than deconstructing an argument, it is making a mistake. The risk of logical assumptions or errors is too overwhelming to not deconstruct every belief.
The reality of God
The conversation manages to converge after a while on the issue of God, but just barely. Although the three men in this discussion are fairly diverse, philosophically speaking, they can all just barely agree on God. Yes, there must be some transcendental explanation for reality and order, but after that fundamental belief, they immediately disagree again, and they do not really converge again afterward. The book is a commentary on religion, and yet there is only one agreed-upon religious confession in the entire piece. This irony is close to the meaning of the discourse.
Religious belief as evil
The inverse opposite to skepticism is religious belief, and if Philo is arguing that only skepticism makes good philosophy, then his opinion about religious belief is fairly controversial. Ironically, he sees religious belief as a kind of immoral device by which a person gets to skip the actual work of proving one's ideas. Instead of proving the beliefs to be either true or not necessarily true, some people in this imaginary community prefer blind loyalty to the beliefs which are common in the day.
The ironic student
For Hume and Philo, Hume's closest representative in these Dialogues, the student Pamphilus is ironic. Instead of a Socratic situation where the student is brought forward in their enlightenment, young Pamphilus does what to him feels "right." He maintains loyalty to his teacher despite better arguments from Philo. The loyalty shows something through irony—ironically one cannot arrive at Philo's opinions by loyalty to any point of view. One arrives at Philo's point of view by absolute loyalty to skepticism and independence of thought. Young Pamphilus was doomed from the moment he assumed Cleanthes would be automatically correct about anything.
