This study explored the personality traits and habitual domains of Mencius. Among the philosophers of the Hundred Schools of Thought during the pre-Qin Dynasty era, Mencius was the primary successor and developer of Confucianism. Two thousand years ago, Mencius had already proposed ideologies and discourses that were highly advanced for the period. These ideologies comprised concepts, such as “the interests of citizen exceed those of the monarch in importance”, “prioritizing ordinary citizens” and “life originates from sorrow and calamity, but complacency and pleasure lead to death”. The transcendent ideologies and personality of Mencius were closely related to the teaching style that was adopted by his mother, who chose and persisted in exceptional conduct. Mencius is considered the Enneagram Type 1 personality (i.e., Perfectionist). His core circuit patterns demonstrate the adherence to principles and order and the pursuit of perfection. Mencius comported himself according to these ideals, dedicated to justice and goodness in his daily conduct. Driven by his core circuit pattern, Mencius was able to distinguish right from wrong, good from evil, and measured everything in the world according to this high moral standard. The habitual domains of Mencius comprise striving for perfection, practicing filial piety, fighting for ideals and excellence, and emphasizing the value and meaning of life.