Sect is a fundamental scheme of astrology that provides a foundational basis for how nearly all astrological doctrine operates, including determining which planets will act most favorably and be the most challenging in a given natal chart, how and where each planet functions most optimally and naturally in various schematics of dignity, and even how to approach certain timing techniques from a technical standpoint. The original greek term is hairesis, meaning choice or selection, meant to identify one’s intellectual ‘choice’ and was used for a school of thought in philosophy or medicine. Sect refers to the division of the seven traditional planets into two teams or factions—the diurnal sect, or day team, and the nocturnal sect, the night team.

One of the most foundational pieces of astrological tradition is the Thema Mundi, the mythic chart of the creation of the universe. The Thema Mundi is the theoretic birth chart of the universe that illustrates harmonic order of the planets situated in their domiciles, providing an arrangement that acts as a teaching tool for the most fundamental concepts that astrology is constructed around.