How Did Placidus Become the Most Popular House System?

Episode 244 features an interview with Anthony Louis about the history of how Placidus became the most popular system of quadrant house division used in western astrology in modern times. In late 20th and early 21st century astrology Placidus is the most popular house system, and it is usually the default house system in most software programs, which makes it the system that most people begin their studies of astrology with. The question is: how did this come to be the case? Especially since there are other forms of quadrant house division that are available, such as Porphyry or Alcabitius houses, what led to the widespread acceptance of Placidus? It turns out, the origins of the Placidus house system and its popularization lie in the 17th century, and it was partially based on an an attempt to reinterpret a controversial passage from the work of the 2nd century astrologer Claudius Ptolemy. The genesis of this discussion was an article on Anthony's blog titled Why are Placidus Houses so Popular? Our goal here was to talk about some of the arguments outlined in that post, and go into some areas in greater detail, to understand the history of house division. While our previous episode on the origins of the different forms of house division in ancient astrology covered the early history of house division, the purpose of this episode is to fill in some missing pieces about the later history from the Renaissance era forward into modern times. You can find out more information about Anthony on his website: TonyLouis.wordpress.com Below you will find an extensive set of show notes that we used as the outline for our discussion. This episode is available in both audio and video versions at the bottom of the page. Episode Outline and Show Notes Here is part of the outline we created in preparation for this episode: Based on Anthony’s November 2019 blog article Why are Placidus Houses so Popular? Follow-up to original article: “Placidus: The Default Darling of Domification”, in Federation of Australian Astrologers Journal, Vol 49, No 2 (June 2019), pp. 21-26. Premise of the discussion: In late 20th and early 21st century astrology Placidus is the most popular house system In modern western astrology. It is the default house system in most software programs, like Astro.com As a result of that it is the system that people usually start with One of the questions that comes up is why is Placidus the default quadrant system? Holden makes a passing remark that Placidus became the default due to availability: “It has become a cliche in the 20th century that the Placidus system later became the 19th and 20th century standard because it was the only one for which affordable tables were readily available. This is partially true, but the same thing could be said for the initial success of the Regiomantanus system.” Holden, A History of Horoscopic Astrology, p. 150. Anthony took some issue with this because Placidus had been popularized earlier. While it was the primary system available by the 20th century, this was because it had been promoted widely since the 17th century. So how did this get started? Placidus published his book in 1650. Focused on primary directions and house division. He was interested in reconstructing Ptolemy’s approach. Part of the general back to Ptolemy movement. Also evident in Lilly and others. Ptolemy was the oldest Greek author available Viewed as the most authoritative. Ptolemy has a discussion of house division in his length of life chapter (3, 11). This is also where he introduces primary directions. The method of house division he advocates here has long been the subject of dispute. “This one chapter has occasioned more astrological controversy than any other ever written.” Holden, A History, p. 47. Ptolemy was like the Einstein of his day