The traditional Chinese official system of the central government was rather precocious. In the Western Zhou Dynasty, court officials were classified into the two levels of lords and ministers. The former consisted of the Grand Guardian (taibao, 太保), the Grand Preceptor (taishi, 太师) and the Grand Astrologer (taishi, 太史) in the early period, but only the Grand Preceptor and the Grand Astrologer later, with the position of the Grand Preceptor possibly occupied by two officials simultaneously.