Why are Placidus Houses so Popular?

British astrologers were captivated by the brilliance of Placidus and began a deliberate campaign to popularize his concepts and methods in Western astrology, especially in the English-language literature. The Roman Catholic Church was terrified by the ideas of Placidus (just as they had been by the ideas of Galileo), and the Church banned his writings in the Catholic countries of Europe. Prior to the popularity of Placidus in Protestant England, Regiomontanus was the dominant House system among British astrologers, including William Lilly.

Recently I watched a YouTube video about house systems in astrology. This otherwise helpful video on astrological house systems contains a glaring error. The idea that Placidus became popular in the West only because tables of Placidus houses were so readily available in an urban legend that was propagated initially as an astrological joke by knowledgeable historians of astrology. (I can recall both Rob Hand and James Holden joking about this idea a couple decades ago.) Unfortunately less well-informed astrologers took this joke as the truth and began to spread this myth as if it were factual.

Let me be clear that I am not singling out the presenter of this YouTube video for criticism. I don’t know her or the quality of her work, which may be excellent. She has merely fallen into the trap of widespread misinformation about the reason for the popularity of Placidus houses in the English-speaking world. My goal is simply to clarify a historical fact as well as some of the theoretical rationale for Placidus Houses.

trump placidus
This is a sample natal chart cast with Placidus Houses, the most popular system in Western astrology.  Astrologers who falsely claim that Placidus houses became popular only because their tables were readily available are living in an alternate reality.  Such a distortion of historical fact could be considered “fake news” by today’s journalistic standards.

In reality it was the British astrologers who popularized Placidus houses because the writings of Placidus were banned by the Roman Catholic Church and only available in Protestant England. Until that time Regiomontanus was the dominant house system in the West because of the false belief that Regiomontanus correctly understood Ptolemy. The British astrologers, upon reading Placidus, realized that Regiomontanus had misunderstood Ptolemy (considered the father of Western astrology at the time) and that Ptolemy was in reality using the method described by ibn Ezra in the 12th century and espoused by Placidus in the 17th century to time primary directions.

Because the British astrologers regarded the teachings of Placidus (who in many ways anticipated Einstein’s notion of a space-time coninuum) as a major breakthrough in astrological research, they discarded the tables of Regiomontanus, which were available in England (Lilly has them in his horary text) and began a campaign to popularize Placidus and his ideas, which they felt more correctly represented the origins of Western astrology. Unfortunately modern astrologers who don’t know the history of Western astrology and therefore don’t understand the joke which claims that Placidus houses only became popular because the Placidus tables were readily available are perpetuating a false view of reality.

While it is true that the Placidus  Tables of Houses of Dalton and Raphael were the ones that were widely available in the 20th century, this does not mean that the availability of tables is what made Placidus popular. Rather, it was a deliberate decision by British astrologers to give up Regiomontanus and promote Placidus because they were impressed with his writings and felt that he more accurately represented the original ideas of Ptolemy in his understanding of house division and primary direction. In other words, Placidus did not become popular because the tables were available. It was the other way around. The tables were made available because of the immense popularity of Placidus’s writings in England. In his book on Primary Directions Martin Gansten does a great job documenting the tremendous impact of Placidus on British astrologers after the epoch of William Lilly who favored the Regiomontanus system as did his contemporary Morinus in France.

A final note about the logic of the argument.  Would one say that fast food is popular in the USA because there are 16,000 McDonald’s outlets in this country? Or is it more likely that there are so many McDonald’s restaurants because fast food has become so popular? Hint: Replace “fast food” with Placidus House System and “McDonald’s” with Tables of Houses in the previous two sentences.

Addendum (30 Nov 2019): Response to Kevin Lopez’ request for references.

Astrology was immensely popular in England in the 17th century when William Lilly published his Christian Astrology (1647), which begins with Tables of Regiomontanus Houses. These tables remained available in his book in various British libraries during the following centuries. With the advent of modern science and the scientific worldview, interest in astrology waned considerably in the 18th century.

Placidus published his Physiomathematica sive coelestis philosophia  in 1650. The works of Placidus, a professor of mathematics and astronomy at the University of Pavia, were placed on the Church’s Index of Forbidden Books in 1687. Good Catholics could only read the works of Placidus at risk of eternal damnation of their souls. Nonetheless, word of the innovative ideas of Placidus had spread throughout Europe, and the astrologers in Protestant England had access to books banned by the Pope in Rome. Perhaps it added to the appeal of Placidus’ writings that the Church did not want anyone in Catholic Europe to know what the brilliant scientist and monk was talking about. This was the same Church that had condemned the works of Galileo several decades earlier.

I suspect that Placidus (1603 – 1668), a university professor of astronomy and physics, was influenced in his thinking about astrological houses by the work of his astronomical predecessor Johannes Kepler (1571 – 1630) who propounded his second law of planetary motion that planets sweep out equal areas in equal times. I recall a homework assignment in my university astronomy class in which the teacher asked us to show the mathematics which Kepler used to derive his laws of planetary motion. As I did the assignment, I was reminded of the theoretical basis of Placidus houses in which the areas of the houses are determined by the amount of time that elapses along the diurnal semiarc. Kepler, by the way, used his careful study of the orbit of Mars to derive the theoretical principles of his laws of planetary motion in which he, like Placidus and Ptolemy, seemed to be implicitly aware of the importance of taking into account the fact that we live in a space-time continuum.

It is important to note that Placidus did not invent the system of houses that bears his name. Rather, he popularized the system of houses described by the the 12th century Hebrew astrologer Abraham ibn Ezra, who argued that this house system was the original one described by Ptolemy in his Tetrabiblos. Placidus agreed with ibn Ezra and therefore provided the scientific justification for the use of “Placidus houses” based on the writings of Ptolemy.

A 17th century English translation of a book by Placidus appeared in 1657, which made his ideas available to a British audience. Other translations appeared in the late 18th and early 19th centuries. Perhaps the most influential English translation of Placidus was published by John Cooper in 1814 at the beginning of the 19th century.

One of the most influential British astrologers to adopt Placidean teachings was John Partridge (1644-1715). Like the British astrologers before him, Partridge learned astrology using the accepted standard of Regiomontanus houses, as did Lilly and Gadbury who were famous astrologers of this period. In his work An Astrological Vade Mecum (1679) Partridge begins his book with Tables of Regiomontanus Houses. This book was available in British libraries during the following centuries, so that British astrologers could have used the Tables of Regiomontanus Houses from the books of Lilly or Partridge if they had wished to continue the tradition of Regiomontanus houses in the 19th and 20th centuries. Thus, the claim that only tables of Placidus houses were available in the 19th and 20th centuries is patently false.

At some point after 1679 Partridge discovered the works of Placidus and became a zealous convert to the ideas of Placidus. In 1693 he published his Opus Reformatum: Treatise of Astrology in which The Common Errors of that Art are Modestly Exposed and Rejected in which he rejected Regiomontanus houses in favor of the ideas of Ptolemy as explained and clarified by Placidus.

Two other British astrologers of the period, Richard Kirby and John Bishop, published a book The Marrow of Astrology in 1687 in which they explicitly rejected Regiomontanus in favor of Placidus. To quote from the introductory materials of this 1687 book in which they reject Regiomontanus (bold and blue color mine):

“The marrow of astrology in two books : wherein is contained the natures of the signes and planets, with their several governing angels, according to their respective hierarchies : also philosophical reasons for takeing the planets antiscions, and part of fortune, with the method of directions according to the Ægyptians and Chaldeans, with several other useful examples : also a new table of houses, exactly calculated for the latitude of London, with tables of the mundane aspects, and all that is requisite, for the rectifying and directing nativities, according to the true intent and meaning of Ptolomy : wherein is discovered the errors of Argol, Regiomontanus, and most of our modern authors, in several examples, never before done in English / by Richard Kirby and John Bishop”.

To stress another important point, the Regiomontanus Tables of Houses were available in England in the 20th century, despite claims of some modern astrologers to the contrary. For example, in 1852 Zadkiel (aka Richard James Morrison, 1795-1874) published his famous abridged version of Lilly’s original 1647 text Christian Astrology under a new title: An Introduction to Astrology. Zadkiel clearly had a copy of Lilly’s original text with its Tables of Regiomontanus Houses but he deliberately eliminated the Regiomontanus tables from the 1852 abridged version of Lilly’s text because of the then current acceptance of Placidus and his teachings. Zadkiel could easily have incorporated Lilly’s Regiomontanus House Tables into the new abridged text because they were readily available to him, but he chose to include Placidus Houses instead because he believed that Regiomontanus was in error in his understanding of Ptolemy, who was regarded as the final arbiter of classical astrology.

Summary: In the late 1600s, after the death of William Lilly, the ideas of Placidus, which were condemned by the Catholic Church, found a receptive audience in Protestant England. Several British astrologers, including Partridge, Kirby and Bishop, began an active movement to reject Regiomontanus houses in favor of Placidus because they believed that the brilliant Italian monk and professor of mathematics had correctly explicated the ideas of Ptolemy, one of the founders of Western astrology. As a result, they published tables of Placidus Houses to make them readily available. At the same time, the tables of Regiomontanus Houses remained available in books by Lilly and in the earlier works of Partridge (before he rejected Regiomontanus). There was a deliberate decision to stop using Regiomontanus houses, which were now regarded as a misunderstanding of Ptolemy, and instead to use the houses of ibn Ezra as popularized by Placidus. As an aside, it is interesting to note that Placidus houses have made their way into Indian astrology, which primarily uses whole signs, in the so-called K.P. system developed by the late Professor K.S. Krishnamurti.

Addendum, 22 February 2020:

On 21 February 2020 I participated in the recording of a podcast with Chris Brennan regarding this topic.  This edition of the Astrology Podcast is due to be published by the end of February 2020. In response to a question Chris raised about Zadkiel’s abridged version of Lilly’s Christian Astrology, which I couldn’t answer at the moment, I have posted the following response Zadkiel’s Rejection of Regiomontanus Houses.

About Anthony Louis

Author of books about astrology and tarot, including TAROT PLAIN AND SIMPLE, HORARY ASTROLOGY, and THE ART OF FORECASTING WITH SOLAR RETURNS.
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11 Responses to Why are Placidus Houses so Popular?

  1. kevin lopez says:

    I believe what you say, but where should I look for documented evidence that English astrologers assessed the Placidus house system vis a vis Regiomontanus and opted to use Placidus instead of Regio?

  2. Hi Kevin,

    Thanks for the question. No need to believe what I say without evidence. Astrologers often say things that they can’t justify and simply believe things because of some bias or opinion that is not empirically or historically grounded. Later today (30 Nov 2019) I will do an addendum to the above post with some references so you can see how I derived my argument. I’ll also try to supply some links so you can read the original sources.


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