SoSoG

SoSoG is an acronym for 'Standing on the Shoulders of Giants', a metaphoric expression (also used by Isaac Newton) for a reference list of selected 'classics' of secondary anthroposophical literature that supplement Rudolf Steiner's GA life work and provide a foundation for spiritual science.

The giants are the anthroposophists who worked in the wave of spiritual science around the central work of Rudolf Steiner for more than a century.

The idea is to develop a reference library as a foundation for spiritual science, covering all domains.

In short: the GA is some 350 volumes. That was by one person a century ago.

Suppose we want to complement this GA with a library of say 200 books of 'must-have' complementary secondary literature, that would be a flanker to the GA, as a foundational library for anthroposophy .. what would those be?

Background

Many students into anthroposophy dive into the tremendous body of lectures and books by Rudolf Steiner .. but some often stop there.

However, Rudolf Steiner was not alone but was surrounded by many important Individualities who incarnated in the same timeframe to contribute to the new impulse of spiritual science, and contributed a tremendous wealth of exceptional materials, thereby already structuring and further exploring certain subject areas, complementing them with own research. For a selection, see Schema FMC00.586 and variants on the topic pageanthroposophists.

In the past 120 years a tremendous amount of work was done in this respect, yet

• a) this work is not always very well known (one has to really search and find its way);
• b) one can easily be 'snowed under' by many thousands of book titles in databases of anthro libraries.

So: where to start? How can we benefit more from what exists? broaden our horizon

The SoSoG list of secondary literature: foundation library for spiritual science

The list contains recommended 'classics', 'must-haves' or 'must-reads' for the earnest student of spiritual science who wants to build a personal library, or deepen knowledge in a certain area.

The choice was made to limit the SoSoG list below to english books, but note there is a wealth of secondary literature in german which is not included here. More works are being translated however, and some german anthro reference works are due for translation and will be added. In the current list this is the case for G00.005 and G00.011 that have been translated for years now (by the FMC initiative), but are still awaiting publication.

The list covers a broad variety of topics across many fields, yet is far from being exhausive. Quite on the contrary, these books are listed because they provide a basis or introductory foundation in any area - so they are a starting point for study and reference.

The SoSoG list

Schema FMC00.396 is an overview list on the SoSoG classics as explained on this page (Standing on the Shoulders of Giants). This is the very first version to initialize the concept, it will be updated regularly. Note the translations table on the right has been is not complete, so languages and versions are surely missing at this stage.

Please Contact us if you want to contribute, see below.

Commentary

The list below is ordered chronologically based on the year the work was written. One needs to take into account the timeline of publication of Rudolf Steiner's lectures, and the fact people only had access to a limited set of cycles. Even after the start of the GA initiative, new cycles were still published after the 1970s that contain key material that authors hardly had any access to (even though certain people went to research topics directly in the Dornach archive before materials were published).

Note the 1950s saw the publication of a number of 'classics' that remain foundational upto today.

The 1920s-30s

• G00.001 - Elisabeth Vreede: Astronomy and spiritual science (2007, letters 1927-30 first in DE in 1954 and first in EN in 1980)
  • This appears to be the only published work by Vreede, the key astronomer in the group directly around Rudolf Steiner.
  • Also in FR as 'Le ciel des dieux: Lettres sur L'astronomie' (1999), in NL 'Antroposofie en astronomie' (2019), in DE 'Astronomie und Anthroposophie'
• G00.002 - Gerbert Grohmann (1897-1957): The Plant (1974 in EN, original in DE in 1929 as 'Die Pflanze als dreigliedriges Wesen in ihren Wechselbeziehungen zu Erde und Mensch')
  • a classic by the pioneer of anthroposophical botany , with many editions
  • language availability: DE, EN, FR, IT
    • La plante: une approche de sa vraie nature (1978)
    • Tra sole e terra. La vita delle piante

• G00.003 - Hermann Poppelbaum: Man and animal (1931 in EN, 1931 in DE as 'Mensch und Tier')
  • language availability: DE, EN, NL, ES
    • Hombre y animal
    • Mens en Dier
• G00.004 - Norbert Glas: Reading the face (2008, first DE in 1935)
  • This is the first of Glas' many works on physiognomy, others are on the temperaments, hands, feet, hair, etc). It is a base work in this area.
• G00.005 - Maximilian Rebholz: Systematic anthroposophy (1936)
  • translated by the Free Man Creator initiative, awaiting publication

The 1950s

After WWII had cleared up, the 1950s brought a series of books that have become 'classics' in any anthroposophical library. They were written by the many great figures that incarnated in the wave 1890-1910 to pick up anthroposophy and brought the work of their study out after the second WWII part of the 30-year war (1914-44) that shook the world.

• G00.006 - Rudolf Hauschka: The nature of substance (2008, original in DE 1950 first in EN 1966)
  • This book brings across the scientific value and rigour of Hauschka, his scientific tests, imaginative insights, perspectives and applications.
• G00.007 - Ernst Lehrs: Man or matter (2014, original in 1951)
• G00.008 - George Adams and Olive Whicher: The plant between Sun and Earth (1982, first in 1952)
• G00.009 - Walther Cloos: The living earth (1977, first DE in 1958)
• G00.010 - Wilhelm Pelikan (1893-1981): Healing Plants (Vol 1, 2, 3) (original in DE: 1958, 1962, 1978)
  • language availability: DE, EN, FR, IT
    • original in DE: Heilpflanzenkunde (or: Heilpflanzen-Kunde. Der Mensch und die Heilpflanzen).
    • Homme et les plantes medicinales (1990 and again 2002-2003)
    • Le piante medicinali. Per la cura delle malattie.
      • Per assicurare più vita all'uomo in connessione con la natura
      • La relazione tra la pianta e l'uomo
• G00.011 - Iwer Thor Lorenzen
  • wrote the first set below
    • Metamorphosen, Bd. I/II, Hamburg 1958;
    • Grundprobleme der Evolution, Bd. I/II/III/IV, Hamburg 1958/1959
• G00.012 - Wilhelm Pelikan: The secrets of metals (1973, original in DE 1959)
  • Rudolf Steiner's references to metals, so important as a 'language' in alchemy upto the middle-ages, are scattered in snippets across thousands of lectures in the GA. Here is a unique book giving a logical and coherent coverage of the different metals, and their workings in Man, on Earth, and in the cosmos. With metals we mean not the solid but also the more rarified, highly diluted versions of the key metals.
  • Translations: available in DE, EN, IT, NL
    • 'I sette metalli. L'azione dell'essenza metallica sul cosmo, la terra, l'uomo' (2014)
    • De geheimen van metalen (2006)
      

The 1960-70s

• G00.013 - Theodor Schwenk: Sensitive Chaos (the creation of flowing forms in water and air) (2014, original in 1962 and first in EN in 1965)
• G00.014 - Oskar Kürten: Symphonies of Creation (The Primal Elementary Kingdoms in the Work of Rudolf Steiner) (2018, first in DE 1970)
  • a book which is rather unique in it's scope and coverage of the Elementary Kingdoms, inspired by the work and essays of Maximilian Rebholz who was the first to coin together a deep understanding and the importance of this topic. Kürten goes to cover the different cosmological aspects and workings of the different spiritual hierarchies and entities that make up the fountain of creation, and an understanding of the Elementary Kingdoms is a key closing stone for this. Rudolf Steiner's coverage of the topic in his books and lectures was very limited, and there is no literature on this topic - at all - except for Rebholz and Kürten.
• G00.015 - Wolfgang Schad: Threefoldness in Humans and Mammals: Toward a Biology of Form
  • published in 1977 in EN as 'Man and mammals: Toward a biology of form', with base work in DE 1971 as 'Säugetiere und Mensch. Zur Gestaltbiologie vom Gesichtspunkt der Dreigliederung' with new DE edition 2012)
  • this book was published by Adonis Press in a limited 'interim' expanded version as 'Understanding Mammals' which the author didn't have the chance to fully review. That complete review did happen eventually, and let to the publication of a new two volume work with a new title: 'Threefoldness in Humans and Mammals: Toward a Biology of Form'
• G00.016 - George and Gisela O'Neil: The human life (1998, ch 1-9 published 1977-81, first book edition 1990)
  • unique book in its multi-facetted coverage of the various aspects of the human life in all its aspects and different cycles. A must have to reflect on life's stages, and doing biography work.
  • language availability: EN, DE, FR, ES
    • in FR as 'La vie humaine - saisir le sens de son parcours terrestre' (1996)
    • in DE as 'Der Lebenslauf: Lesen in der eigenen Biographie' (2014)
    • in ES as 'La Vida Humana: Comprender tu biografía' (2019)
      

The 1990s

• G00.017 - Lawrence Edwards: The vortex of life (2006, first in EN 1993)
  • Here is a humble teacher who brings a major contribution to the study of the etheric formative forces, with an original discovery based on diligent experimental work. See also
• G00.018 - Roy Wilkinson: Rudolf Steiner - an introduction to his spiritual worldview, anthroposophy (2005, first in three booklets 1993-4)
  • What book would you give to someone who is open to have a first read on anthroposophy, by means of introduction? This is such an excellent, well written introduction, very readable and recommended for 'novices' to get acquanted with key chapters of anthroposophy.
• G00.019 - Hans-Werner Schroeder (1931-2016): The cosmic Christ (2010, first in 1997 TBC)
  • The study of the Christ from a spiritual scientific and cosmic perspective may be the most important subject we devote our soul work to. But is there a book which spans the arc and shedding light on the multiplicity of perspectives? There are not many, for sure. This is a good compendium of various perspectives of this deepest of all subjects. Of course it can not be complete, but it is still unique in providing a systematic and balanced overview as an entry point and reference, without going in detail.
  • language availability: DE, EN, FR
    • Le Christ cosmique: contribution à la connaissance et à l'expérience du Christ (2017)

Post 2000

• G00.020 - Dankmar Bosse: The mutual evolution of Earth and humanity (2019, first in DE 2002)
  • This is a study volume, a reference to have to accompany one in a life of interest and deepening study. It is a beautiful A4 hardcover book with many wonderful pictures and illustrations, well laid out. A work of love and decades of dedication here by a geologist who lays out the evolution of the earth. See also the work of Iwer Thor Lorenzen on this theme.

Process

1 - Request for input (RFI)

The SoSoG list above, as shown in table FMC00.396, is embryonic and merely to initialize the idea, it obviously needs to be extended.

What books do you feel are 'classics' (or have that caliber), have stood the test of time, provide a unique value add to Rudolf Steiner's work, and therefore belong in the foundational library for spiritual science?

Please send us an email via the Contact page with your suggestions about books for the SoSoG list. Or comment via the Talk page here (requires registration).

Considerations

• Please note that the value and impact of a book is not the same as a 'monument of anthroposophy'. Of course there are very many famous and grand anthroposophists, but the idea is NOT to get them all on the list.
• Rather, the perspective is to assemble the book list to cover the whole scope of anthroposophy, and all its different areas, with key works that have laid out the territory for that domain after Rudolf Steiner.
• Furthermore, please consider there are 'too many' books: if one is not selective, the result will be a list of thousands of books, and not a few hundred max, which is the intention here (also given the size of the GA library).
• Hence, in order to select a book for this list, one needs to take the perspective of a University Faculty that oversees the whole scope and selects the books that are best suited for students. That is why the current list includes as well: introductory books (Wilkinson G00.018), study essays (Rebholz G00.005), overview introduction books (Schroeder G00.019), reference works for a lifetime of study (Schad G00.015 or Bosse G00.020).
• Last suggestion: take the perspective that we are doing this for youngsters who are born now, or who are in their 20s, to offer them an 'map' for orientation, so they have 'a way into' the vast secondary literature of spiritual science. To discover the richness of the century of legacy in the most effective way, not having to plough through search engines of library database and the too many books of unknown anthroposophists (they can do that later), but at least to be welcomed. It is an act of courtesy.

.

2 - Further candidates

Informal input to date also gave:

introductory books - worldview spiritual science

Introductions

• Written for novices or outsiders not familiar with Steiner's own work, or who may find his own works complex or overwhelming, these writers have set out to distills the essential points and core concepts from anthroposophy into a readable, modern format by way of introduction. the below go further than the easy-to-read Wilkinson G00.018 (240p) which is more introductory. Note there have been many dozens of writers who have set out to do this, and written such books, the below is a selection: .
  • Francis Edmunds: An Introduction to Anthroposophy - Rudolf Steiner’s Worldview
  • Robert A. McDermott: The New Essential Steiner - An Introduction to Rudolf Steiner for the 21st Century (300p)
  • Henk van Oort:
    • 'Anthroposophy: A Concise Introduction to Rudolf Steiner’s Spiritual Philosophy' (85 pages)
    • also wrote: 'Anthroposophy A-Z, a glossary of terms relating to Rudolf Steiner's spiritual philosophy' (130 p) .
  • Stewart C. Easton:
    • 'Rudolf Steiner: Herald of a New Epoch'
    • The way of anthroposophy (< 100 pages)
    • 'Man and world in the light of anthroposophy' (540 pages)
      • a very readable and complete introduction on anthroposophy
  • Owen Barfield: The Case for Anthroposophy
• Various others in this category:
  • Jens Heisterkamp: 'Was ist Anthroposophie? : Einladung zur Entdeckung des Menschen' (124 p)

Introductions to Rudolf Steiner's base works

Rudolf Steiner's own base books like Philosophy of Freedom, Theosophy, Outline of Esoteric Science, and Knowledge of the Higher Worlds, meanwhile date back from a time more than a century ago, and these also did not go into the vast breadth and practical application areas that Steiner lectured about in the later stages of the twenty year period 1904-1924. So certain people have written introductions to reading Steiner, and/or introductory selections compiled excerpts for a first dive.

• Christopher Bamford: 'Encountering Rudolf Steiner - Introductions to Essential Works'
• Robert A. McDermott: 'The Essential Steiner - Basic Writings of Rudolf Steiner'

.

etheric and formative forces

.

• Nick C. Thomas: Space and Counterspace - A New Science of Gravity, Time and Light (2008)
  • the culmination of a lifetime of work with an ambitious new view on the whole of physics, advanced and not for everyone, but unique in its nature .

epistemology and Goethean science

• Henri Bortoft: The Wholeness of Nature: Goethe's Way of Science (1996)

3 - About the G-numbering

The G-numbering is a simple sequential number so there is a reference list available in Excel, and these books can be referenced easily on this site, thereby referring to their status, and - in the future maybe or hopefully - also a dedicated page with more extended coverage, that each of these certainly deserve. Such page could include an overview of available editions and translations, reviews, and an author profile and/or links to the author bio pages.

There is no meaning in the G-number, the concept of the list was initialized by the first set of books that embody the idea, the counter currently stands at: 20.

Input process log and notes

We are grateful to people for the following input:

1. Clopper Almon (Feb 2019)

author of a.o.

• A Study Companion to An Outline of Esoteric Science (1998)
• A Study Companion for Rudolf Steiner's Lectures on the Gospel of Mark (2016)

wrote:

As for classics,

• the one that I cared enough about to translate myself is Friedel Lenz, The Picture Language of Folktales.
• Wolfgang Schad, Man and Mammal, now superseded by Understanding Mammals is important. [see G00.015]
• Emil Bock, The Three Years is helpful.
• Pelikan on herbs is also valuable. [G00.013]

Of books originating in English,

• Owen Barfield's Worlds Apart and Saving the Appearances are highly thought of in the literary world. I enjoy his not especially anthroposophic History in English Words.
• Arthur Zajonc's Catching the Light is fascinating.
• George Adams and Olive Whicher, The Plant between Earth and Sun is eye-opening. [G00.006]
• Lawrence Edwards The Vortex of Form is amazing. [G00.015]
• I like everything I have read by Craig Holdrich, though he sticks strictly to careful observation of phenomena. 
• The Recovery of Man in Childhood by A. C. Harwood is a classic presentation of Waldorf Education.

.. I wish I could recommend an anthroposophic book on economics, but I have yet to find one both sound and interesting.

2. Francois De Wit (Mar 2024)

author of the anthroposophical periodical newsletter 'De Brug' and website www.vrijgeestesleven.be (NL)

wrote: ... books I completely re-read twice:

• Dieter Brüll (1922-1996)
  • Der anthroposophische Sozialimpuls. Ein Versuch seiner Erfassung (1984) also in NL 'De sociale impuls van de antroposofie'
  • The Waldorf School and the Threefold Structure (The Embarrassing Mandate: The Risk of Being an Anthroposophical Institution) (in EN 1997, in DE 1992 as 'Waldorfschule und Dreigliederung (der peinliche Auftrag: Vom Risiko, eine anthroposophische Institution zu sein)

Further notes

Note 1 - More on SoSoG

The SoSoG approach links the following main angles:

• a topic taxonomy
• a 'best of' selection or 'gallery' of anthroposophists you should know, or are worthwhile to study. See eg the kulturimpuls website.

The SoSoG gallery or "library of must-study monuments of anthroposophical literature" can be split into the following parts:

• books that have become classics, available in modern editions in English - see below.
• books that have not been translated, were only published in German, and may no longer be available (but only through antique book shops such as booklooker.de). A further subsection consists of material that was not even published in book form, but as newsletters privately published by the author.

For the second category, the FMC project also has an initiative to publish Advanced Study Volumes in English, to make the valuable work of certain anthroposophists available more broadly, mainly when they are of the level that this certainly belongs in an advanced library on spiritual science.

For more info, see also the PDF file in the References section of Status of planned publications

Note 2 - Secondary literature on this site

Certain topics have Schemas to provide an overview list on literature on the topic, just as Schema FMC00.396 above.

These schemas obviously have the structured XL list behind them that can also be made downloadeable.

Examples are:

• History: Schema FMC00.398
• The life of Rudolf Steiner: Schema FMC00.365 (bios) and Schema FMC00.366.jpg (memories)
• Elementals of nature: see Schema FMC00.144 on Elementals of nature

Note 3 - Systematic work - examples of Study Volumes

The following people have published secondary anthro literature 'reference works' in Study Volumes format, and/or have worked in a systematic work on aggregation of the contents in the GA.

See the kulturimpuls website for profiles and more info.

• Ernst Hagemann,
• Maximilian Rebholz, Iwer Thor Lorenzen, Oskar Kuerten
• Otto Hartmann, Fred Poeppig, Wolfgang Schad .. were proliferic writers (and worked also through publishing newsletters)
  .

Examples of what one can call 'rigourous' work:. Let it be clear that quantity and quality are two different dimensions, so the below is just to show how rigourous handling can result in reference works (especially in German culture, whereas for example in the AngloSaxon/English culture the coverage and writings will be more synthetic and concise). They are added here because if one is really serious about a study topic, such reference works provide a foundational basis for one's personal study, as authors have spent many years or most often decades of their life to study it before us. So the coverage overview, bibliography, etc provide a reference for orientation and structuring our thinking about a study topic or field.

• Werner Greub: 'Wolfram von Eschenbach und die Wirklichkeit des Grals'
  • wrote three volumes (1974 to 2004), of 482+570+434+411 = 1897 pages)
  • more on Holy Grail#References and further reading
• Ewald Grether: 'Der Mensch und sein Schicksal im Lichte der Anthroposophie'
  • published three volumes in 1986, printed typoscript format for a total of 501+276+539 = 1316 pages)
  • more on Karma or destiny#References and further reading
• Friedrich Oberkogler: 'Faust von Johann Wolfgang von Goethe ; Werkbesprechung und geisteswissenschaftliche Erläuterungen'
  • published two volumes in 1981-82 of 423+735 = 1158 pages
• Norbert Glas (1897-1986) spent his life interested in human physiology, he published his first books in 1935-38 (and these were republished in 1961-63) but continued studying various aspects and publishing them in booklets (upto 1981, 85, 87). In total there are 8 volumes for a total of 747 pages.
• Stefan Leber (1937-2015): 'Menschenkunde als Grundlage der Pädagogik'
  • three volumes published 1986, for a total of 1808 pages, as a foundational work on the knowledge of the human being (in context of Waldorf education)
• Karl Heyer was a historian, he published nine volumes between 1939 and 1958 on the various ages
• Friedrich Husemann, Otto Wolff: Das Bild des Menschen als Grundlage der Heilkunst
  • Vol 1 and 2 of 1974: 1082 pages
  • Vol 2: 475 pages
  • Vol 3: 624 pages
• more recent examples of people publishing comprehensive overview works are Frank Linde (Auferstehung) and Uwe Buermann (Karma)

Note 4 - Considerations regarding secondary anthroposophical literature

1- Values and personality of the author expressing in 'atmosphere' of a work

Study materials can be looked at from different angles. There is the first and foremost the contents, but then also the format, and this note is about the personal values and personality of the author that find expression in, or are reflected in the work.

Here's a quote from a letter by a reader from Germany (edited):

On the one hand, there's the content is correct ... the other aspect is the atmosphere that emanates from the whole thing.

A good source for in-depth anthroposophical essays is the "Mitteilungen aus der anthr. Arbeit in Deutschland". I can only recommend it.

Well, in one issue I found an essay by Hella Krause-Zimmer and by Gunhild Kacer, both on the subject of Christmas and the two Jesus boys. There was nothing wrong with the content of either essay, and yet Hella Krause-Zimmer's essay is much clearer and more sober, while Gunhild Kacer's essay creates a completely different atmosphere. You can sense the religious atmosphere of the Christian community. 

Yes, judging texts and people is also about personal taste. But I think there should also be an objective element to it.  When you meet people in person, you very quickly get the feeling: I can trust this person. And you will certainly share this feeling with many people, even if not with everyone. When it comes to trustworthiness in anthroposophical matters, it is of course more difficult.  

Take the example of Peter Selg: he has written a huge biography of Steiner, but because of his tendency towards hagiography, one has to take it with a grain of salt. This tendency towards hagiography can be a gateway for errors and misjudgements. Then there are authors who want to write something sensational, who surround themselves with an aura of importance and great significance, like Prokofieff.

Thus, overestimation of oneself, exaggeration (Selg, von Halle, Prokofieff) or ideological bias (Zander) or one's own agenda (priests of the Christian community) can create gateways for one-sidedness and errors.

Nevertheless, these people can also be right on individual points and these must then be acknowledged. Wimbauer spoke of layered judgment.

But as I said, these are personal assessments and you can only assess this kind of quality if you are "qualified" to do so

There are obvious cases where this has led to serious polarization, see: Polarization and polemics within the anthroposophical movement

Certainly people with some unqualified clairvoyant capabilities have been writing from their experience, but it was not always well received also because there was no way of judging or assessing, or things were just too unbelievable to be acceptable.

This topic has been explicitly covered by certain anthroposophists, eg W.J. Steiner wrote about the importance of conscientiousness, similarly Rebholz and Kürten wrote about the importance of staying truthful to understanding literal statements with context instead of going off on interpretations.

2 - Critical view on Rudolf Steiner as a source

Given that anthroposophy depends greatly on the huge amount of information and insights provided by Rudolf Steiner, a tricky subject is the consideration to accept that Rudolf Steiner too could make mistakes.

Again a reader quote to introduce the topic:

It requires courage, and who will tell if one is right or wrong?

Some authors make this consideration, but without a concrete specifics to back up such statement, so only as a defensive shield, a means of claiming objectivity for one self.

In reality the Master was not allowed to err. Because if he was wrong here, what about the other points, where do we stop?

An interesting example is the so-called Critical Edition. Here lectures and contents is scrutinized and held against the contemporary current worldview and scientific views, in order to assess and give a critical view. However critique in most cases comes from a lack of understanding and insight in what is really meant or described. If the ingoing position is to take a different approach towards science, then it is obvious that one will only find points to critique and be critical about.

Rudolf Steiner often raised this point of epistemology from various angles: Hegel vs Kant, the Goethean vs Baconion approach to doing science, the difference in worldview. See a.o.

• Relationship between mineral and spiritual science
• Top five problems with current science
• Worldview wars

At the same time, Rudolf Steiner clearly pointed out that anybody including himself will only see thusfar, and with time this line of view naturally shifts [lecture reference not clear, but he gives the example of Aristotle]. This to explicitly state the intrinsic limitations of all he brought.

Relevant in this context is GA069A about truths and errors in spiritual investigation, see eg 1912-11-27-GA069A (continued the next day) ... "I tried today to describe not only the possibilities of error finding spiritual truth, but also the possibility of error with the dissemination of spiritual truths."

3 - Source attribution

Related to that is the origin of source materials. Like with paintings that are attributed to a master but without anyone can be really sure.

GA 40A contains a number of poems that are attributed to Rudolf Steiner but are not by him. It was possible to find the real authors in each case. In this context, the German term Duktus is also used. Often it is also simply the language, the ductus, the style that make it clear that it is not a text by Steiner

Related pages

• Anthroposophists
• Study volumes
• Navigating anthroposophical resources
• Sources of spiritual science
• The Michaelic stream

References and further reading

• Ernst Hagemann: 'Bibliographie der Arbeiten der Schüler Dr. Rudolf Steiner'