The Alethiometer, also known as the "Golden Compass," is a fictional device from Philip Pullman's His Dark Materials series. It is used to discern the truth by interpreting symbols on its face, allowing the user to ask questions and receive answers through the movement of its hands. The Alethiometer operates on a principle of intuition and understanding, requiring the user to develop a deep connection with the device. It is often wielded by characters like Lyra Belacqua, who learns to read it over time, showcasing themes of knowledge, truth, and the quest for understanding in the narrative.