Both of these mystery novels share one common denominator: the use of logic as the most important skill to enable our inherent biases to deconstruct and see things for what they really are. Parting from this statement, the argument of appearance versus reality is also a shared theme, for this is what moves the plot forward, putting the two investigators, Hercule Poirot, and William of Baskerville in an ongoing search for symbols and cues that would lead to the solution to each of their mysteries. One thing that both novels have in common is the stylistic tendency of having more than one story going on at the same time. Instead of a linear style of storytelling, the plot branches out into smaller stories of people and their issues, taboos and secrets. All of these are essential elements of the detective story which color the tone and keep the attention of the audience.
Symbolism and logical thinking- These two topics come hand in hand in the novels and serve as a very strong bonding theme. In The Name of the Rose the mysterious deaths of so many friars seem to revolve around the only copy of Aristotle's second book of Poetics, on Comedy. The mystery of this book did nothing for William, as he did not attribute any powers to it that would lead the friars toward their deaths. Rather than selling out to the idea of a "dangerous book", he looked deeper into patterns, attitudes, and history of the institution that he was investigating. He paid particular importance to symbols, which reflects Eco's deep commitment to semiotics. This is what led him to ask the right questions, find the right patterns, and key into what was really going on: someone had purposely poisoned the book of Comedy in aims of trying to prove that laughter can kill the body and the soul; that man is only meant for self-punishment and sacrifice. Hence, those who read the book would die, not because of the book, but because of the wetting of their fingers to be able to pass the poisoned pages.
In The Murder of Roger Ackroyd a similar situation occurs where a cast of colorful and dysfunctional characters make them all potentially capable of murdering..anybody. Some of them are neurotic, all are rich and feel a sense of entitlement, they gossip, they back-stab one another, and the rumors make it almost impossible to see who was the true murderer of Ackroyd. Most importantly, the conundrum of personalities and eccentricities found in King's Abbot make even the motif of the murder to become gray. Again, we see how the main character focuses on logical steps, on facts, on attitudes, personalities, and patterns to determine the killer. This time, it was the most unthinkable character, as it was the narrator of the story himself who ends up being accused by Poirot despite of the fact that all suspicions pointed to the spendthrift stepson of Ackroyd's, Ralph Paton.
Appearance versus Reality- This theme is the supreme force that permeates throughout the plot of both novels. In The Name of the Rose the nature of the suspects made them all unlikely to be guilty of any wrong doing. Monks can hardly be related to crime and murders, particularly during the Medieval times where most lived in enigmatic silence and simple living. However, there are many hierarchies within the Church, and incredibly, we find that there are also many factions. Those who are progressive and do not condemn the book of Comedy were the victims of the staunch conservatives who insisted that the philosophy if Aristotle was evil in nature. It is this latter faction that hid beneath the cloth of the monastery to do what they did, no matter if it meant to take the lives of others.
In The Murder of Roger Ackroyd money is seen as a tool to buy reputations and innocence, but this is not the case. Poirot uses their superficiality to understand how much they are willing to hide: the need to be superficial entails a need to hide or disguise something else. This leads Poirot to dig deep into the personalities of the characters, as well as into their potential motives. Ultimately, this is how he can figure out the unlikely suspect.
Although different in theme overall, these two novels do show these two themes quite strongly.