Placidus de Titis was an Olivetan monk and professor of mathematics, physics and astronomy at the University of Pavia from 1657 until his death. Placidus popularized the system of astrological houses now known as the "Placidian system", current in modern astrology. He did not invent the method; it is acknowledged by the 12th century Hebrew astrologer Abraham Ibn Ezra as the system employed by Ptolemy, an attribution that was accepted by Placidus.

Most horoscopic traditions of astrology systems divide the horoscope into a number of houses whose positions depend on time and location rather than on date. In Hindu astrological tradition these are known as Bhāvas. The houses of the horoscope represent different fields of experience wherein the energies of the signs and planets operate—described in terms of physical surroundings as well as personal life experiences.