Pursuit and Conservation of KnowledgeThere's an interesting theme throughout the show: knowledge. Specifically, the pursuit of knowledge and how that knowledge is passed on to future generations. Lisa first goes to Dracula's castle to learn how to be a doctor, because as she says, "I've exhausted my other options, and the stories say that the man who lives [in this castle] has secret knowledge." Even though she's heard the stories about Dracula, she still goes to him because she believes that she can learn more from him than from other people. And, considering that most medical "knowledge" in the show revolves around giving sick people dried foot skin, it's not surprising that Lisa would take the chance to go to the castle for the possibility of learning from Dracula.
It's implied that Dracula is a scholar, judging from his extensive collection of books, scientific equipment, and the like. When you're a vampire with nothing but time on your hands, it's understandable that you'd take the time to learn about the world. Because of that, Dracula's been cooking up all sorts of experiments, and even created a teleportation device to be able to move his castle around from place to place. However, he stays in one place and doesn't try to learn about humanity until Lisa nudges him in the right direction. According to her, traveling "as humans do" is one of the best ways to learn about the world. This is a view that's shared by the Speakers, who travel from place to place to collect and share information with others.
While Dracula is traveling to learn about the world, Lisa uses her knowledge to help heal others. However, this knowledge is viewed as witchcraft because the science that she used is indistinguishable from magic to the eyes of many people. It's because of this, along with jealousy and plain hatred, that lead to Lisa being executed by the very people that she was trying to help. It's also the case with the Belmonts, who pursue the knowledge to fight against demons, but they are excommunicated and exiled by the same people they're trying to protect. This idea of a person pursuing knowledge and sharing it with others is one that leads to having a massive target on your back.
However, because of that idea, many people in Wallachia are suffering; they lead short, scared lives defined by sickness and demon attacks. There are a few ways of communicating with other villages, much less countries. The people that have learned about the world have locked themselves and their knowledge away from the rest of humanity, leading to a cycle of fear, ignorance, and persecution that prevents any kind of positive change from happening. Consider that the two main repositories of knowledge in the show are in hidden away places; the Belmont Hold is literally buried underground, and Dracula would sooner stab himself with a stake rather than let a human into his library in his castle.
The group that defies this outlook on life are the Speakers, who view knowledge as a living being that needs to be shared and maintained by humans in order to keep it alive in the world. Instead of keeping their knowledge under lock and key, the Speakers actively put themselves in harm's way to help others. However, the Speakers have some conflicting views on their pursuit of knowledge and how they share it with others. They refuse to write down their stories, but they learn how to read ancient (and forbidden) languages in order to study knowledge. Sypha says that God hates them because they defy the separation of human language and knowledge (from the Tower of Babel), but they fight against demons and vampires and serve no devil. If there is any group that serves as a "neutral" force between God, the Church, and the Belmonts vs. Dracula, vampires, and demons, then the Speakers are that force.
And yet, the Speakers' view of knowledge also has flaws. Sypha tells Alucard that all the Speakers in the world would only be able to retain and share a fraction of the knowledge that the Belmont Hold has. There's also the simple fact that Speakers are constantly in peril, and the knowledge that they possess could easily be wiped out with a zealous mob. Sypha herself says that she thinks the Speakers are mistaken in regards to their methods of passing on knowledge through oral history instead of written history.
Castlevania shows that both of these views about knowledge are correct but flawed. If we look at the history of the area that the show is based in (Europe in the 15th century), the rise of the printing press and the availability of cheap print materials is what expanded the knowledge of the region because it allowed ordinary people to have access to knowledge without having to go to a library or talk to a learned person. At the end of the second season, Trevor gives Alucard the Belmont Hold's library, in order to allow something better to be made out of it. Only time will tell if that will be the case, but if Alucard is able to pass on the knowledge of both his and Trevor's families, then the cycle of fear and ignorance could be broken, preventing more tragedies like Lisa's execution and providing a chance to push humanity into a better future.
A Thematic Flip on the original DraculaOne of the themes in the book Dracula is that modern science and forward thinking triumphs over superstitious fears and ancient magic. That's why Dr. Seward records his diary in a phonograph, Jonathan and Mina Harker write in shorthand (and their journals survive when Dracula destroys the transcribed versions, but not the shorthand), Lucy was almost saved by the cutting-edge science of blood transfusions (so cutting-edge, in fact, that they didn't know that incompatible blood could have killed her), and why Van Helsing is a doctor rather than a vampire hunter. Even when dealing with superstitious means, like staking Lucy, they research every possible way of subduing her and kill her with all of them (the staking scene gets the most credit, but they also cut off her head and fill her mouth with garlic). Thanks to modern record-keeping, they destroy Dracula's secondary lairs, because he had to purchase them through lawyers. Dracula tries to stay modern by moving to Britain and learning perfect English, but he also moves into a crumbling abbey and brings his soil with him.
In this Castlevania, it's the vampires who are scientific, and the rest of the country are superstitious peasants. Carmilla's castle has thermal heating, Dracula's castle and Alucard's hideaway has clockwork and electricity, and Lenore says that long life means that vampires have their own separate culture, complete with philosophy. The most knowledgeable human groups are the Speakers and the Belmonts, who preserve rather than innovate. The Speakers refuse to record their oral knowledge, and the Belmont hold is a cache full of magical artifacts hidden by a magic door of death.
Some other reversals: In the book, Dracula lives alone in a huge, old castle, and takes pride in his warlike ancestors who cut a bloody swathe across Europe. Trevor Belmont doesn't live in the hold anymore, but the Belmont Hold is a huge, old mansion, and generations of Belmonts still remember the clan's founder Leon Belmont, and preserve the skulls of vampires (including children). Book Dracula has nomadic Romani as servants. The nomadic Speakers are mistaken for servants of evil, but are peaceful preservers of knowledge, including magic.