This article defines Dasan’s view on the Seongni debate as “metaphilosophy.” Metaphilosophy is often dubbed the “philosophy of philosophy” or “second-order philosophy.” The word “meta” has Greek origins, meaning “after” or “beyond.” A metaphilosopher stays outside of an ongoing philosophical debate or problem and conducts a second-order review of its nature, purpose, and method, instead of being directly involved in the debate. If a metaphilosopher is defined as such, Dasan, then, can be regarded as the first and foremost metaphilosopher in the Neo-Confucian history of Joseon. Instead of engaging in the intense Seongni debate of his time as a participant, he remained outside the debate and criticized its nature, goals, and methodology from a second-order perspective. As a metaphilosopher, Dasan employed methodological tools, such as linguistic analysis. This article analyzes Dasan’s metaphilosophical stance on the Seongni debate and concludes that his metaphilosophical perspective provided a turning point in the history of Joseon Neo-Confucianism.