Illustration of the Placidian Mechanism of Action

Neither modern nor trigonometric or sophisticated. The rigour of the Placidus method of house division (which dates back to the century of Abraham Ibn Ezra) is predicated upon the exhaustiveness that characterises its search of ascensional times, that is, the account for the seasonal or ascensional time of all oblique or zodiacal degrees, revealing thereby those that will become or occupy the intermediate cusps (not just the four angles). It is therefore distinguished from the other two major time methods of house division, Alcabitius and Koch, due to it constituting a complete or a simultaneously uninterrupted measurement. The Alcabitius and Koch calculations record the seasonal time of only the ascending degree and of only the culminating degree, respectively, whose temporal interval thus established is divided into three equal portions, each of which constitutes the three houses within the quadrant, as opposed to the case of Placidus, whereby said interval will constitute one house only, that of whatever cuspal degree is responsible for that length of time. Our exposition demonstrates unequivocally that each house portrays or represents—or is the product of—the trisection of a discrete ascensional time, that being the ascensional time of the specific cuspal degree in question, rather than solely that of the Ascendant (as in Alcabitius) or that of the Midheaven (as in Koch). All degrees possess relative temporal values, or, more precisely, fixed relative temporal values, inasmuch as each degree maintains or retains its ascensional time, relative to the others, at any given latitude. The Placidus method therefore stands as the sole system naturally compatible with seasonal or planetary hours. The mensuration employed by the Placidus method yields relative houses, as opposed to absolute divisions.