With this article, I shall turn my attention back to the diffusion of the concept of space in architecture, in the first decades of the XX century. Again, this is to show that space should be preferably understood as an ideal entity (to grasp not without epistemological ambiguities) rather than a physical entity existing ‘out there’; an abstract conceptualization or a product of cognitive and linguistic abilities that man applied to the analysis, representation and communication of actual phenomena, and then transformed into a seemingly concrete entity. So, what originally emerged as an abstract concept denoting a simple distance (space: from the ancient Greek term ‘spadion’ or ‘stadion’, see the article Back to the Origins of Space and Place) is now considered by many in the guise of a concrete entity: the fabric of reality in which everything and everybody exists. In this game of references between the actual and the potential, the concrete and the abstract, the physical and the ideal or mental, we find the ultimate ground for architecture, as well as the ground for the concepts of place, space, and man’s understanding of reality.
Continuing what I have commenced in the previous article — Mind, Space, Architecture: On The International Style — I will extend the analysis of the spatial language used by architectural historian Henry-Russell Hitchcock and architect Philip Johnson in the seminal book for architects ‘The International Style’, (1932). In this way, I want to shed some light on some problems that may arise behind the mesmerizing effects of space understood as a privileged way of accessing the complex phenomenon of architecture. It is out of this mesmerizing effect that, in modern times, architecture has been often understood and interpreted as an art and science of space, forgetting what is necessary for any typology of space to exist: place and its processes, which range from concrete to abstract, that is from physicochemical to symbolic, passing through biological, ecological, and sociocultural. In addition, I will also consider the slightly different spatial language adopted by the two authors in a companion text published in the same year: the catalogue prepared for the first architectural exhibition held at the Museum of Modern Art, New York, in 1932 — Modern Architecture: International Exhibition.
Image 01: Cover of the 1932 edition of the book The International Style: Architecture Since 1922, by Henry-Russell Hitchcock, Jr., and Philip Johnson.
The Spatial Language of ‘The International Style’
In the previous article, I specifically analyzed the times Hitchcock and Johnson used the term ‘space’ in the captions that described the images in their seminal book The International Style. Surprisingly, in those concise descriptions that presented modern architecture to a wide audience for the very first time, we have found no mention of the term ‘space’. In the first part of this article, I will look further into that text to analyze more diffusely the kind of spatial language used by the two American authors throughout all of the 260 pages of the 1966 edition of the book. Specifically, I have taken 5 main spatial expressions to understand how could it be possible to speak about architecture without nearly mentioning the term ‘space’, which is now a ‘catch-all’ term or concept to speak about architecture, either we refer to modern architecture or architecture of the past epochs. Those terms are ‘space’, ‘volume’, ‘dimension’, ‘room’, and ‘openness’. Then, how did Hitchcock and Johnson use that spatial terminology in the book The International Style? Did they have the same spatial understanding of architecture we have now? I will quote those parts of the text containing the aforementioned spatial terminology, and make some comments. To understand better the context of the quotations I will report here, I suggest the reader to compare those quotations with the original text: an online freely accessible source of it can be borrowed at www.archive.org
remarkably, when Hitchcock and Johnson wrote “The International Style”, they described the new architecture purely in terms of the old word volume, venturing only one reference to space— ADRIAN FORTY
On Space and Volume
‘emphasis upon volume—space enclosed by thin planes or surfaces as opposed to the suggestion of mass and solidity’.
We find this quotation in the Preface, written by Alfred H. Barr Jr., the first director of the Museum of Modern Art in New York, and the man who appointed Hitchcock and Johnson to organize the first architectural exhibition held at MoMA, in 1932. Here, Barr, an art historian, is presenting one of the three principles of the new international style in architecture identified by Hitchcock and Johnson in the 1930s (the other two principles being ‘regularity as opposed to symmetry’ and ‘the intrinsic elegance of material, technical perfection, and fine proportions, as opposed to applied ornament’). This is one of the few times in the book in which the term space seems to denote architectural space as a form of enclosure. However, in virtue of the other times in which the terms ‘space’ and/or ‘volume’ were used in the text by Hitchcock and Johnson, and in virtue of the specific grammatical construction of that phrase a consideration arises: evidently, if Barr felt the urgency to introduce space as volume (or, better, volume as space, given that ‘volume’ is the main subject of that sentence) it means the term ‘space’ (in the architectural sense) was not acknowledged as a self-independent object yet, or it was not fully grasped in its autonomous architectural value and function we assign it today. In that sentence, there is a fundamental ambiguity, which dissolves when we read it entirely and we understand that the entity we are speaking about is precisely that which is ‘enclosed by thin planes or surfaces’. However, as we are going to see, this clarity of intentions concerning the nature of that which is enclosed by surfaces is an exception, and is not totally consonant with the exposition of the same principle made by Hitchcock and Johnson throughout the pages of the book; in fact, they explicitly used the formula ‘Architecture as Volume’, without mentioning ‘space’ to denote this important character of the new modern style of architecture; behind the two terms — space, volume — there can be important differences, not just analogies in the spatial sense: did architects in the 1930s understand ‘volume’ as the surface of the box — i.e. the material planes of the container — or did they understand it as that which is contained, that is, the contained as ‘space’? We’re going to see how Hitchcock and Johnson answered this question, after the introduction of other quotations concerning ‘space’, and following the same temporal order the term ‘space’ was presented in the book.
‘In the conflict that obtains between the two elements of construction, solidity and open space, everything seems to show that the principle of free space will prevail, that the palaces and houses of the future will be flooded with air and light.’ 
This caption from Apollo by Salomon Reinach (1904) opens the Introduction to The International Style. Similarly to the previous quotation by Alfred H. Barr Jr., in this quotation by Reinach — a French historian and archeologist — the term space is used in a way very similar to the way we are now accustomed to, in an architectural context. Yet, I believe the fundamental question concerning the fully-fledged determination of the linguistic boundaries of space still remains open, for two reasons especially: first, even on this occasion, space has not the power to stand alone; in the circumstance, it is accompanied by the attributes ‘open’ and ‘free’, as if ‘space’ was still a too vague concept to be used alone beyond any possibility of misunderstanding, especially in the architectural domain. Second, on both occasions, ‘open space’ and ‘free space’ are an arbitrary translation from the original French term ‘vide’, which literally means ‘void’ or ‘vacuum’. What is lost and what is gained in the translation from French to English is not my point here, but this is an indication of a certain degree of indeterminacy or ambiguity that seems to be intrinsic to the spatial terminology; very likely, this was the case in the first decades of the XX century. Moreover, the two quotations we have just seen, which apparently may render the idea of the existence of a concept — architectural space — very similar to our current understanding of it, were not pronounced by the two authors of the book. I think we have to look at the way Hitchcock and Johnson themselves used the term ‘space’, or related spatial terminology, to understand better the spatial language of architecture in the 1930s. And even if the book — The International Style — is a specific description of different modern architectures, there are very few occasions where the term ‘space’ or related spatial terminology can assume an architectural meaning in the sense we understand it now (architectural space intended as an immersive and subtle volumetric entity to be modelled by the architect; a kind of transparent block of ethereal matter or ‘a perfectly uniform and translucent block of glass extending from infinity to infinity [which] has all the properties of such a block of glass except the glass’ to say it with the words by the British theoretical physicist Julian B. Barbour — see note  and image 28 in the article Space and Place: A Scientific History – Part One).
Apart from the aforementioned quotations, we can read different spatial propositions which have a more direct denotative power, in a simple dimensional and quantitative sense, like:
‘the spacing of skyscrapers’, and ‘Skyscrapers […] must be so widely spaced that…,’ ;
‘The supports […] are normally and typically spaced at equal distances’;
‘without interfering with the regular spacing of the isolated supports’;
‘where the distance between separate windows is very slight, the space between may be treated as…’;
‘the spacing of letters and words’; ‘the spacing of the standardized windows’;
‘The absolute regularity in the spacing of the supports’.
Concerning the use of terms and expressions like ‘spacing’, ‘spaced’, or ‘the space between’ they all refer to the original dimensional sense of the term ‘space’: space intended as a distance or gap, a linear interval (1D) between elements, rather than an area (2D), or a volumetric and immersive entity (3D or 4D) as we understand it now, when we are in an architectural context, especially. As we have seen in the previous articles, this is the original denotative sense of the term ‘space’ properly — from the Greek ‘spadion’ or ‘stadion’, which, as theThe Oxford Classical Dictionary says, in the very beginning denoted ‘the distance covered by a single draught by the plough’ dragged by a yoke of oxen, before it acquired new senses: a kind of footrace on a medium-short distance, a standard of length or the arena where athletes ran (again, I redirect you to the article Back to the Origins of Space and Place) —, a sense which existed far ahead of the connotative extension of the term in two, three or four dimensions; an extension of meaning out of which the architectural sense of space also emerged, in modern times. The quotations above were only discursive cases in which the term space had a specific and clear denotative function; this is not the architectural sense of space we are interested in and out of which ambiguous spatial interpretations may arise. This is also the sense of the quotation by the English historian of architecture Adrian Forty, which I have put in evidence above and on which we will return shortly.
In the book, we also find expressions like ‘terrace space’ or ‘the wall encloses the interior room space below’, which are closer to the architectural sense of space we usually think of. As concerns the expression ‘terrace space’, I still see a passive function of the term ‘space’: as on the preceding occasions, in this context too, ‘space’ has not the communicative power to stand alone without diminishing the sense of that expression; the companion term is necessary to express a precise meaning: then, the final sense of that expression is more likely conveyed by the word ‘terrace’ rather than by the word ‘space’. In this case, I’d attribute ‘space’ the function of delimiting a region, a surface on the floor rather than a ‘livable space’, intended as an immersive volumetric entity, which is the characteristic sense of space so typical of architecture according to the modern interpretation. In this case, the sense of space is subordinated to the very idea of ‘terrace’. Analogous considerations can be made concerning the proposition ‘room space’: again, ‘space’ is accompanied by another term – ‘room’. However, in this case, I’d say we are very close to the traditional sense of architectural space I’m going to consider right below, with the following expression used by Hitchcock and Johnson:
‘Volume is felt as immaterial and weightless, a geometrically bounded space’.
Here we are, right at the core of the spatial question that interests us, as it is dealt with in the book The International Style: ‘remarkably, when Hitchcock and Johnson wrote The International Style, they described the new architecture purely in terms of the old word volume, venturing only one reference to space’ — Adrian Forty, Emeritus Professor of Architectural History at The Bartlett School of Architecture, says. The quote above is the ‘one reference’ Forty speaks about. The very structure of that phrase by Hitchcock and Johnson is illuminating in the sense argued for by Forty: by retaining the term ‘volume’ as the subject of that sentence they indirectly meant that space was almost considered as a derivative concept a secondary notion with respect to ‘volume’. The focus of the authors was on ‘volume’ — intended as a boundary condition — rather than on ‘space’, as Forty’s observed. Moreover, ‘space’ is not simply space in itself: it is something ‘geometrically bounded’; it is this characteristic understanding of space that redirects us to the term ‘volume’ to express a material boundary; so, with that expression, the attention shifts on the boundary (walls, floors or partitions that delimit the interior volume) not on space, which, in this way, assumes a parasitic existence, almost unnoticed, if not entirely unnoticed (at last unnoticed by the two authors), despite its revolutionary architectural meaning in the modern sense. We will soon return on this ambiguous question, to dissipate any doubt on the spatial or volumetric intentions of the authors.
There are a few other cases in which the two American authors used the term ‘space’ to characterize the sense of the new modern style of architecture. Despite that, considering that we are discussing 260 pages of architectural descriptions, to find such a small number of references to ‘space’ as an interpretative key on how to look at architecture, is quite remarkable, as Forty observed; this is especially true if we consider our contemporary obsessive tendency to speak about architecture in terms of space only. Other references to space used in this specific architectural sense are:
‘the aesthetics of interior space’;
They give scale to the created space’ and ‘It gives to modern interiors a new kind of abstract space design unknown in the architecture of the past.’
The last sentence is especially important other than problematic for the scope of this article: literally, that sentence seems to suggest that the authors were conscious about the existence of a new architectural entity, unknown before, which could characterize modern architecture (not architecture as a whole but interior architecture — this is not a secondary issue for the spatial question). Despite that, there are too many occasions on which the authors fail to see the absolute relevance and the possibilities offered by that new entity, which, now, is what really characterizes architecture and the design practice with respect to the past epochs. This is the main reason why this new entity is directly mentioned just a few times in the book compared to the totality of the times the authors referred to the spatial value of architecture using alternative expressions, and avoiding the direct use of the term ‘space’. I argue this is due to the fact that the epistemological contours of that new entity — architectural space — were still under development, or that that entity was not completely grasped by the community of architects in those days. Given my first-hand experience as an undergraduate student of architecture and as an architect who focused studies and practice on the role that place and space have in architecture (at this regard, I’m preparing an article, in which I will explain how my way of intending architecture procedurally grows out of a continuous come-and-go between placial and spatial dimensions), I can say that one thing is to possess information on the spatial interpretation of reality and architecture, another thing is to consciously and proactively use that spatial information as an architectural instrument to produce a new kind of architecture or simply beautiful architectures: you need the genius of Frank Lloyd Wright, Mies van der Rohe, or, more recently, Zaha Hadid to consciously turn an abstract instrument like space into concrete examples of high quality, spatially-driven architectures. This discrete leap of the imagination is expressed by the term ‘emergence’, properly: architectural space and space before it are emerging concepts. Specifically, I believe that, after the spatial findings of Descartes and Newton (with the invention of analytic geometry Descartes formalized the existence of geometrical space, while with the invention of absolute space Newton tried to formalize the existence of physical space), what we now understand as ‘architectural space’ needed a couple of centuries of preparatory epistemological investigations, through different domains (from geometry to astronomy and physics, from philosophy and psychology to art), before being elaborated as an independent concept, specific to the architectural domain.
Slideshow (Images 02, 03, 04): Endless House, models, 1960, Friedrich Kiesler.
Slideshow (Images 05, 06, 07): Heydar Aliyev Center, Baku, Azerbaijan, 2007-2012, Zaha Hadid Architects.
There are a few other occasions on which Hitchcock and Johnson used the term ‘space’ in the book:
‘it is possible to take care of them [the rooms of an apartment] in much less space’.
‘Curved and oblique interior partitions, moreover, often make possible the more complete adjustment of available space to function’.
‘Isolated supports interfere hardly at all with free space and circulation’.
In all of those cases, the first and second especially, space has a quantitative, dimensional function, almost a neutral geometric function in two-dimensional sense (space as a floor area), rather than a qualitative connotation typical of architectural space intended as a three-dimensional or tetra-dimensional expanse — the vehicle of events and information (physical, phenomenological, social, symbolic, etc.).
Finally, they also used the term space to define the free extent of a field or a landscape, in the following occasion:
‘As far as possible the original beauties of the site should be preserved. Mere open spaces are not enough for repose’.
Of course, this is not the type of reference to space so typical of the architectural domain, where space is often seen as an interior entity (from a historiographical point of view, architectural space was born as an interior entity, deriving its identity or nature from a tectonic act of enclosure, to use an expression borrowed from the German architect and historian Gottfried Semper; the very understanding of space/volume as a ‘geometrically bounded’ entity — as Hitchcock and Johnson say — is an indication in that sense). That quotation should be also an alert about the fact that ‘space’, as an entity in itself (I mean ‘space’ when used in the material sense), has little physical meaning, if no meaning at all: obviously, ‘mere open spaces’ are vacuous entities — a mere no-thing. What kind of vacuous entity can positively affect our minds or bodies? No-thing like that; that’s why ‘mere open spaces are not enough for repose’.
... “Architecture as Volume”. That was at best an ambiguous phrase since volume is properly “contained space”.— HENRY-RUSSELL HITCHCOCK
Concerning the difference between ‘space’ and ‘volume’, which we have already anticipated in a section above, the ambiguity of the formula ‘ARCHITECTURE AS VOLUME’ was distinctly grasped by Hitchcock and Johnson only after the publication of the original edition of The International Style (1932). In fact, in an article written for the August 1951 number of the magazine Architectural Review (and added as an Appendix to the 1966 edition of The International Style), Hitchcock wrote: ‘It is worthwhile, none the less, to consider here a particular principle of the International Style as we saw it in 1932, notably the one concerning “Architecture as Volume.” That was at best an ambiguous phrase since volume is properly “contained space”, while we were then chiefly concerned with the avoidance of effects of mass in the treatment of the exteriors of buildings.’ I think those words are a clear indication that, in the 1930s, ‘space’, either in the sense of a practical or theoretical tool for architecture, was not grasped yet as a clear-cut and independent architectural concept. At least, this was true for Hitchcock and Johnson, since their focus was on the material qualities expressed by the boundary conditions of a building, this is how ‘volume’ was understood. However, this does not mean that architectural space was not present in the cultural goings-on at that time and that particularly sensitive architects, critics, historians or scholars couldn’t have already grasped its importance and implications for architecture. Indeed, we know from many sources that that concept was certainly in the air since the last decades of the XIX century, thanks to the converging considerations and perspectives on space by philosophers, historians, architects, artists, and artistic movements. Concerning this important question for architects — the different historical phases that offered architecture an interpretation in the spatial sense — I have added a brief Appendix, at the end of this article.
It may be worthwhile noting that in the article of 1951 in which Hitchcock commented on The International Style twenty years after its publication, in the light of new developments in modern architecture, the aforementioned quotation is the only one containing a direct reference to the term ‘space’. Then, those words by Hitchcock exclude an interpretation of architecture in the spatial sense in favor of an interpretation in the volumetric sense (more explicitly: their focus was on the containing box — the exterior surfaces — rather than on the contained space-as-volume, as also Adrian Forty said). We should keep those illuminating words in mind to disentangle the seeming ambiguity that may result from reading the following spatio-volumetric expressions used in the text:
‘architecture as volume rather than as mass’ 
‘The effect of volume began to replace the traditional effect of mass’ 
‘In the early evening, when the lights come on, the solid tower like quality of the skyscraper disappears. Then, at least, it is seen as one volume divided up into horizontal storeys.’ 
‘an architecture that is not mass but volume.’ 
Image 08: Barcelona Pavilion, Barcelona, Spain, 1929, Mies van der Rohe.
I think we should consider with the utmost interest the spatial or, better, the volumetric terminology used by Hitchcock and Johnson to describe the architectures of Mies van der Rohe, who is probably the first and greatest example of how space could have influenced the modern conception and interpretation of architecture:
‘the absence of volumetric enclosure in Mies’s pavilion’. 
‘In the Barcelona pavilion the walls are screens but they do not define a fixed volume. The volume beneath the post-supported slab roof is in a sense bounded by imaginary planes. The walls are independent screens set up within this total volume, having each a separate existence and creating subordinate volumes’; 
‘Mies’s country-house project of 1922 […] very evidently does not fit either the principle of enclosed volume or the principle of regularity’. 
The first statement appears in the Foreword to the 1966 edition, written by Henry-Russell Hitchcock. Significantly, instead of speaking about the immanence of ‘space’, which is the hallmark of Mies van der Rohe’s pavilion in Barcelona (an interpretation which is now very common between architects, especially after the interpretation the famous critic and historian of architecture Siegfried Giedion gave of that building in another seminal book for architects: Space, Time, and Architecture, originally published in1941), the author speaks about ‘the absence of volumetric enclosure’. This is in agreement with what we have just seen: the focus of the authors of The International Style was on the ‘volume’ — the superficial/material boundary that determines the visual quality of architecture, especially — rather than on space itself.
Images 09-10: Brick Country-House, project, 1922, Mies van der Rohe.
Concerning the second quotation on Mies’s country-house, it is difficult for a contemporary reader not to see ‘space’ behind the term ‘volume’. As I said in Mind, Space, Architecture: On The International Style, today it would be almost impossible for an architect, historian, or critic of architecture to describe Mies’s Pavilion (or its neoplastic antecedent, the 1922 project for a country-house) without making any explicit reference to the term ‘space’. On that occasion, Hitchcock and Johnson seem to have done what today we could consider a tightrope walking exercise to avoid the use of the term ‘space’ to describe the Barcelona Pavilion. However, considering the totality of the spatial and/or volumetric expressions used in the book, the explanation could be more direct than a mere linguistic exercise: maybe there was no intentionality at all in avoiding the use of the term ‘space’ since, as I anticipated above, that concept was not a fully-fledged conceptual tool to be used beyond any epistemological ambiguity; so, they ultimately preferred to avoid its use, relying on a more traditional architectural vocabulary and conceptions. But there is also another possibility: in that specific occasion, they may have intentionally avoided the use of the term ‘space’ retaining a sort of negative explanation (the absence of volume enclosure rather than the presence of space), given that ‘volume’ (the material surfaces) and not ‘space’ (that which is enclosed by the surfaces) was one of the three core principles they individuated for the new style. Overall, we cannot exclude that the two authors could have already glimpsed into the possible architectural value of ‘space’ as a brand new tool for architecture. I say this especially in virtue of the fact that concurrently with the architectural exhibition held at the Museum of Modern Art in New York, a catalogue was also published (with the title Modern Architecture: International Exhibition). In that catalogue, which we will analyze in a paragraph below, the formula ‘surface of volume’ that we find many times throughout the pages of The International Style was replaced either by the term volume or, above all, by space, thereby using a technical language (a spatial language) closer to our current spatial conception. But this complicated question concerning the spatial language used by Hitchcock and Johnson in the 1930s is not over: to render the overall complexity of this question, in a pamphlet prepared in 1931 for the Museum of Modern Art to announce the first architectural exhibition to be held the following year, Philip Johnson did not characterize the essence of modern architecture referring to its spatial or volumetric value. I argue that, given the broader intent of that pamphlet and the not yet clearly established value of the term ‘space’ with respect to actual architectures, the author decided to focus on other elements especially: functional, economic and structural elements determining what has been improperly popularized as the aesthetics of the white box, which characterized the initial stage of modernism in architecture.
Concerning the descriptions of Le Corbusier’s buildings (who, together with Gropius, Mies and Oud, is considered by Hitchcock and Johnson one of the four pioneers of the international style) the focus of the authors is more easily traceable to the interpretation of ‘volume’ as the superficial effect of the bounding surface, while every connotation of volume as space that we could derive from those descriptions, is more a suggestion that spontaneously arises in the mind of contemporary readers, so used to decades of spatial interpretations in architecture, especially since the second part of the past century (we cannot forget that Le Corbusier himself, in his Towards a New Architecture — originally published as Vers Une Architecture in 1923 — speaks of ‘mass’, ‘surface’ and ‘plan’ as the ‘three reminders to architects’). So, for example, with reference to Le Corbusier’s Ville Savoy we read: ‘Some strive to arrange all the elements of their design within a single bounding shape, thus emphasizing to the utmost the unity of volume of the given building’. While concerning the description of another building by Le Corbusier, we read:
‘In the Le Pradet house by Le Corbusier […] the enclosing volume is defined by the continuous slab roof. The exterior surfaces are not continuous…’.
Image 11: Maison de Mandrot, Le Pradet, France, 1931, LeCorbusier.
Apart from the aforementioned explicit pronouncement made by Hitchcock against their interpretation of volume as space in The International Style, the volumetric interpretation (in the material sense, concerning the exterior surfaces which form a volume) is confirmed many times in the text by expressions like:
‘The models Van Doesburg made of houses in the early twenties, in collaboration with other Neoplasticists, with their abstract play of volumes and bright colors…’.
‘These buildings would have been pure volume, glazed cages supported from within’.
‘the effect of a single volume with continuous surfaces’;
‘The very effect of volume that is sought in choosing surfacing materials can easily be diluted or contradicted by bad fenestration’;
‘The clarity of the impression of volume is diminished by any sort of complication’.
‘if the stucco is rough, the sharpness of the design, which facilitates apprehension of the building’s volume, is blunted’;
‘the use of different colors […] emphasizes strongly the effect of surface, but it breaks up the unity of volume’; 
‘Its walls are usually the interior surface of the same protecting screen which constitutes the exterior surface of the architectural volume’; 
‘With skeleton construction enveloped only by a protective screen, the architect can hardly avoid achieving this effect of surface of volume’.
Concerning the last sentence, the expression ‘surface of volume’, or ‘surfaces of volumes’, is used many times throughout the pages of The International Style,so that it could be probably considered the most direct and unambiguous formulation of the first principle of the modern architectural style enunciated by Hitchcock and Johnson, were it not for the fact that the same expression is totally absent in the catalogue they prepared for the exhibition.
Further analyses of the spatial language used by the two authors in a volumetric sense cannot avoid us pointing out the utmost ambiguity of that vocabulary, and noting that possible disclosures of new spatial horizons of meaning are inherent in that language; so that the presence of one entity — space — naturally resides in the expanse left vacant by the other entity — volume; in this way, space takes within itself or absorbs the very essence of the term volume. For us, contemporary readers and architects, to imagine the co-presence of two entities (volume-the container, space-the contained) behind one word (volume) is almost unavoidable in propositions like:
‘The effect of mass, of static solidity, hitherto the prime quality of architecture, has all but disappeared; in its place there is an effect of volume, or more accurately, of plane surfaces bounding a volume’;
‘the great majority of buildings are in reality, as well as in effect, mere planes surrounding a volume’;
Volume as surface let volume as space emerge so that volume/space, or the visible/the invisible become complementary parts of the same architectural phenomenon; so tight is the link between space and volume that the authors seem to have identified the new element (architectural space, precisely) even if they keep calling it ‘volume’, in the following occasions:
‘the inside of the volume of the building’
‘the whole volume inside a building’;
‘It is interesting to compare the Citrohan house with Wright’s Millard house in Pasadena, designed a year [or two] later. Note the similarity of the volume-concept of the interior’
On Planes in Three Dimensions, Rooms and Openness
Concerning other spatial propositions adopted in The International Style, on a few occasions the authors used the alternative expression ‘planesin three dimensions’ instead of using planes in ‘space’ as a more direct (and modern) spatial expression. Possibly, this is another indication that goes in the direction we have observed since the beginning of this article: in the 1930s space was not a ready-to-use concept to communicate architectural experiences. Again, in these cases, the focus is on the materiality of the surfaces or planes that compose the facades of buildings (hence, on the volume-as-material surface) and not on the immateriality conveyed by the three dimensions, understood as an autonomous architectural entity, which still goes unnoticed:
‘He [F.L.Wright] also was the first to conceive of architectural design in terms of planes existing freely in three dimensions rather than in terms of enclosed blocks.’ 
‘On the analogy of abstract painting he [J.J.P Oud] came to realize the aesthetic potentialities of planes in three dimensions with which Wright had already experimented’;
Another spatial term frequently used in the book was ‘room’. In nearly all of those occasions where that term is used, it has a specific detonative character, and not the generic function we would use today to describe a generic volumetric extension, inside the building, which is almost independent of the function assigned to that ‘volumetric extension’ (this geometrical or dimensional extent without active agency is ‘space’, properly); therefore, many times we read about ‘press-room’ , ‘dining rooms’, ‘bathroom’, ‘living room’ or ‘outdoor living rooms’, or ‘bedroom’.  Other architectural descriptions use more generic expressions like ‘room’ or ‘rooms’, ‘different rooms’, ‘enclosed rooms’ or ‘public rooms’, ‘subordinate rooms’ or ‘common rooms’ which more easily may suggest (to the current-day reader) the idea of a neutral ‘space’ behind the term ‘room’. But it is especially in a couple of descriptions concerning the architectures of Mies van der Rohe and Wright, that ‘room’ seems to be a substitute for ‘space’:
‘The absolute regularity in the spacing of the supports does not prevent wide variety in the placing of wall screens to form separate rooms’ — the authors say concerning Mies’s Barcelona Pavilion. 
‘An onyx spur wall separates the library on the left from the drawing room on the right, but does not interfere with the open feeling of one large room. Black or white velvet curtain on chrome rails can separate the rooms more completely’, — they say with respect to Mies’s Tugendhat house.
‘The plan Wright prepared for a house to be built for himself in 1903, incorporating all the living areas except the kitchen in one articulated flow, is obviously an early prototype of the one-room houses’, — Henry-Russell Hitchcock says in the Appendix (1951). What is that ‘one-room houses’ if not what we now describe as an ‘open space’?
Finally, I point out another series of spatial expression where terms like ‘openness’, or related terminology in the form of attribute or verb, could be thought of as traditional substitutes for the more technical ‘space’, or simply they evoke a spatial dimension, which we would now probably understand or express in terms of ‘space’ directly, rather than as ‘openness’, which is a more generic term without necessarily expressing a specific architectural value. So we read:
‘His [F.L. Wright] open planning broke the mould of the traditional house’.
‘His [LeCorbusier] plans, however, were even more open than those of Wright’.
‘Thus he [Mies] achieved, still with the use of supporting walls, a greater openness even than Le Corbusier with his ferroconcrete skeleton construction’.
‘The prime architectural symbol is no longer the dense brick but the open box’.
‘interiors which open up into one another without definite circumscribing partitions’.
‘The second storey, as shown by the plan, includes the open terrace within the general volume’, they say concerning the design of Ville Savoye.
‘Mr. Johnson, not only used a tower-like cylinder inside his house of glass in New Canaan, but contrasted the ultimate openness of the main house with a guest house of brick almost as solid in appearance as if it had no interior whatsoever’, Henry-Russell Hitchcock says in the Appendix, 1951.
Image 12: Brick House and Glass House, New Canaan, Connecticut, 1947-49, Philip Johnson.
Image 13: Modern Architecture: International Exhibition, catalogue, New York, 1932
With the analysis of the spatial language used in the catalogue prepared by Hitchcock and Johnson for the MoMA 1932 exhibition ‘Modern Architecture: International Exhibition’, we find in the middle of a quagmire from the standpoint of its spatial language: if we compare it to the book The International Style, the year of publication is the same, 1932, yet the spatial language adopted in the catalogue is slightly different from that in the book. Specifically, while we have seen that the interpretation of architecture in terms of ‘space’ was almost absent in The International Style, in the catalogue things changed somewhat: so, for instance, the typical expression ‘surface of volume’, which the authors used in The International Style to express one characteristic element of the new international style, was replaced either by the terms ‘volume’ or ‘space’, using a spatial language closer to our days rather than to the vocabulary used in the volumetric/mass tradition. Overall, the ‘volumetric interpretation’ which is present in the book as the antagonist of the old ‘mass interpretation’, seems to have been complemented by (or evolved into) a ‘spatial interpretation’, in the catalogue. What changed in the passage from the book to the catalogue? I will consider the position directly expressed by Hitchcock in the Foreword to the 1966 edition of The International Style and I will point out some quotations from the catalogue, where architectural descriptions utilize a more explicit spatial terminology (click on the link contained in the description of Image 13, above, to be redirected to the MoMA’s website and download a copy of the catalogue).
We have to remark two things: first, the difficulty to put architecture into a few categorical principles, as in the intentions of the authors; second, the precise historical moment in which the exhibitions, the book and the catalogue were programmed and realized (1931-32). As Hitchcock directly explained in the Foreword to the 1966 edition of the book, the architectural production in that precise historical moment was ‘a flowing stream’ and things could have gone differently had they written the book ‘several years earlier’ or just ‘a few years later’. It means in those years the interpretation of architecture reflected that fluid situation and some executed works and their acceptance among architects, critics and architectural historians might have changed the interpretation of architecture even within a short period, emphasizing elements until then hidden or overlooked. Specifically, Mies’s Pavilion in Barcelona, more than his Tugendhat House or LeCorbusier’s Ville Savoye, could have marked a point of epistemological demarcation concerning the spatial interpretation of architecture, with respect to its interpretation in the volumetric sense. This volumetric interpretation was what the authors were interested in since it was the ‘volumetric’ character (the material surfaces that enclose a volume) that they indicated as a contradistinctive mark of architecture since the 1920s (remember the extended title of the 1932 edition of the book is The International Style: Architecture since 1922). In that Foreword, Hitchcock admitted they had difficulty in fitting Mies’s Pavilion into their basic descriptions, but they couldn’t avoid its inclusion in the book because that building was acclaimed as ‘perhaps the supreme example of architectural design’ in those years — this is what we directly read from Hitchcock —, and because Mies was included in the book as one of the four founders of the international style, together with Gropius, Oud and LeCorbusier. I suspect that in the book, which was more dogmatic and universal in character compared to the catalogue, they had to describe Mies’s work according to their limited number of universal principles (volumetric, not spatial), stretching their interpretation as ‘volumetric’ in a negative sense (as we have seen in a quotation above concerning the Pavilion, they speak of the absence of volume rather than the presence of space). Then, the dogmatic and universal character of the book against the more flexible and receptive character of the catalogue accompanying the exhibition is a possible explanation for the different spatial vocabulary: one inclined to defend a limited number of principles (therefore, using a volumetric vocabulary even in circumstances where a spatial vocabulary might have been more appropriate), the other more open to differences and receptive to the architectural reality of the moment. If we consider this question from an opposite perspective, that is if we consider the attribution of a spatial character to what until a certain moment was interpreted according to mass or volumetric principles — which is what really happened in the interpretation of architecture with historians like August Schmarsow, Alois Riegl or, later, Sigfried Giedion and Bruno Zevi —  this should make us reflect on the arbitrariness according to which we now interpret any type of architecture in the spatial sense, either modern or past architectures, considering ‘space’ a privileged, if not the unique, way of accessing the phenomenon of architecture.
Another reason which can motivate the slightly different spatial/volumetric terminology between the book and the catalogue could also be traceable to the specific author in charge of writing or describing the different architectures in the different parts of the catalogue (here, I refer to the different sensibilities, backgrounds and interests of Hitchcock and Johnson, with respect to the spatial/volumetric question); while the original 1932 content of the book was a double-handed work (apart from the Preface, written by Alfred H. Barr, Jr.), the catalogue is divided into different sections, each one written by a specific author. The descriptions that mark a conceptual and linguistic discontinuity in spatial terms with respect to the book are those written by Philip Johnson, especially; and they concern the works of Mies van der Rohe and of LeCorbusier by contrast to Mies. So, Johnson writes:
‘In his peculiar treatment of space and in his keen sense for decoration and materials Mies is unique. For him a building is a series of partially enclosed spaces opening into one another and opening to the exterior without the intervention of a solid screen as a defining facade. The planes which define these spaces he makes independent and apparently intersecting by the use of a different material for each plane…’.
‘Le Corbusier, even in his earliest house, made his interiors of one space which could be subdivided. He kept, however, the simple outer rectangle in his plans. Mies tendency, on the other hand, is to extend the house to include part of the outdoor world, doing away with the continuous outside wall.’
Concerning the aesthetic innovations of the Barcelona Pavilion, Johnson writes: ‘The new element is the rigidly regular system of steel posts and the simple rectangular roof slab, which replace the arbitrary brick walls and irregular roof slab of the earlier project. Space flows around this rigid system. Partial screen walls, so placed as to create the feeling of space beyond, form separate rooms. The posts stand away from the walls in order to allow freedom of planning and to emphasise aesthetically the rhythm of the structure. So strong is the feeling for one space, rather than separate rooms, that Mies often continues the wall screens beyond their intersections except at the four corners of the entire plan.’ 
‘Bound up with Mies feeling of space is his feeling for the qualities of the planes which divide that space. He dislikes cheap materials…’
‘As an artist of the plan, as a decorator in the best sense, as a creator of space, he has no equal.’
This conversion towards a spatial interpretation against a volumetric interpretation is also evident in the description of the model of the Tugendhat House, which was present at the exhibition. Johnson says: ‘…the living section contains many rooms which form in effect one space. The composition is developed not only by the partitions within this space but also by the fine materials of which these partitions are composed: onyx, macassar wood, velvet and silk. The design especially on the street side shows Mies tendency to make of the roof slab more than the top plane of an enclosed volume. It becomes an independent unit under which walls may divide the space.’ 
With this interpretation in the spatial sense, Johnson makes explicit the aesthetic novelty of Mies’s work: planes-and-space are now the new distinctive and complementary entities (two polarities) of modern architecture; they replace the old polarities planes-volume (or, going even backwards in time, surfaces-mass) as described in The International Style. With Mies van der Rohe, space — or, better, the interpretation of architecture in terms of space — replaces either volume (the characteristic element through which interpreting modern architecture according to The International Style) or mass (the characteristic element through which interpreting traditional architecture).
From Hegel’s embryonic observations on the spatial value of architecture — he considered ‘the space of the interior [as] an enclosure’ to differentiate the Greek classical temples from the Gothic churches —, to Karl Bötticher’s analysis of the influence of spatial organization —Raumeinrichtung — on the shape of buildings (1846); from Gottfried Semper’s concept of direction (or body’s movement in depth) and tectonic enclosure (1851) — which indirectly encouraged a shift of the focus from the materiality of walls and facades to the immateriality of space, allowing next generations of historians and architects to identify the concept of spatial enclosure as a specific architectural tool —  to Camillo Sitte’s idea of physiology of space perception and of exterior space (1889) as opposed to the idea of interior space deriving from the concept of spatial enclosure (he understood that apart from interior space, a tectonic enclosure also produces exterior space, hence urban design could also be understood as an art of space, or Raumkust), passing through philosophical, psychological, artistic, and architectural considerations on the spatial form and perception, especially undertaken by German philosophers, historians, artists and architects like Robert Vischer, Theodor Lipps, Alois Riegl, Albert Erich Brinckmann, Adolf Hildebrand, Herman Sörgel, Fritz Schumacher and many others, in the period between the last decade of the 19th century and the first decades of 20th century; from August Schmarsow’s groundbreaking idea of architectural space, that is, of architecture as a ‘spatial construct’(Raumgebilde), expressed in a famous essay of 1893, where he explains his theory of ‘spatial creation’ (Raumgestaltung), to the architectures of Hendrik Petrus Berlage (‘the art of architecture resides in the creation of spaces, not in the design of facades’), Peter Behrens, August Endell, Frank Lloyd Wright, Adolf Loos — who shifted his initial focus from matter to space, inventing a brand new spatial technique, the Raumplan, for house interiors —, Walter Gropius, Ludwig Mies van der Rohe (‘architecture is the will of an epoch translated into space’ is now a famous motto), in part LeCorbusier, and the theoretical works of artists and movements like van Doesburg and De Stjil, Moholy-Nagy and Bauhaus, in addition to others architects, artists and movements in the first decades of the 20th century; from Rudolph Schindler’s Manifesto of 1912 — where he says that ‘architectural design concerns itself with “space” as its raw material ’ —  to Geoffrey Scott’s pronunciation about the three dimensions of space as ‘the very centre of architectural art’ in the well-known 1914 book The Architecture of Humanism , and to Sigfried Giedion’s writings on the history of architecture explained as a history of the conceptions of space — most notably the well-known ‘Space, Time and Architecture’, 1941; from Nikolaus Pevsner’s (in-) famous imprimatur on the spatial value of buildings and their relationship with architecture — ‘Everything that encloses space on a scale sufficient for a human being to move in, is a building; the term architecture applies only to buildings designed with a view to aesthetic appeal’ —, to Bruno Zevi’s enthusiastic ode to space — notably the book ‘Architecture as Space’ (1964), where he says that architecture consists in ‘the enclosed space in which man lives and moves’ —, architecture has been mainly understood and explained in terms of space, relegating traditional material values to mere epiphenomena.
Image Gallery, (clockwise) – Image 14: Beurs van Berlage, Amsterdam, Netherlands, 1898-1903, Hendrik Petrus Berlage; Image 15: Robie House, Chicago, Illinois, 1908-1910, Frank Lloyd Wright; Image 16: Contra-Construction Project (Axonometric), Gouache on lithograph, 1923, Theo van Doesburg, Cornelis van Eesteren; Image 17: Schröder House, Utrecht, Netherlands, 1924, Gerrit Rietveld; Image 18: Barcelona Pavilion, Barcelona, Spain, 1929, Mies van der Rohe.
 The book was originally published in 1932 with the following title: ‘The International Style: Architecture Since 1922’; it presents the emergence and development of a new style of architecture in the first decades of the past century; this new style, or ‘international style’, has characterized the beginning of the modern epoch in architecture. For the present article, I have used the 1966 edition of the book.
 Henry-Russell Hitchcock and Philip Johnson, The International Style, New York: The Norton Library, 1966. With respect to the original 1932 edition of the book, the 1966 edition is complemented by a Foreword to the new edition and an Appendix consisting of an article written by Hitchcock himself, in 1951, for the magazine Architectural Record, in which — the author says — he made a series of quotations and comments to the old edition ‘in the light of developments in modern architecture over the ensuing twenty-years’ (see Appendix, page 237).
 Ibid., 13.
 Ibid., 13.
 Literally, there is also the possibility to interpret the expression ‘volume—space’ in the phrase ‘emphasis upon volume—space enclosed…’ as one single hyphenated entity (e.g. something analogous to the expression ‘space—time’) and not as the link between two coordinate propositions, but the fundamental question concerning the linguistic ambiguity between volume and space remains.
 Ibid., 17.
 This is the original 1903 French quotation: ‘Dans la lute qui se poursuit entre les deux elements de la construction, le plein et le vide, tout porte à croire que le vide doit l’emporter, que les palais et les maisons de l’avenir, du moins dans nos climats, seront inondes d’air et de lumiere…’, in Salomon Reinach, Apollo: Histoire Générale des Arts Plastiques (Paris: Librarie Hachette, 1903), 115.
 The International Style, 42.
 Ibid., 56.
 Ibid., 64.
 Ibid., 67.
 Ibid., 75.
 Ibid., 161.
 Ibid., 183.
 The Oxford Classical Dictionary, edited by S. Hornblower and A. Spawforth, Fourth Edition, Volume II. (Oxford: Oxford University Press, 2012), 917.
 The International Style, pages 42 and 72, respectively.
 Ibid., 44.
 Adrian Forty, Words and Buildings: A Vocabulary of Modern Architecture (London: Thames & Hudson Ltd., 2000), 268.
 The proposition I have used — ‘how to look at architecture’ — is a reference to the second part of the title of a famous book on architecture written by the Italian historian and critic of architecture Bruno Zevi, who was an advocate of architecture interpreted as a spatial discipline. The book I refer to is Bruno Zevi, Architecture as Space: How to Look at Architecture, 1964.
 The International Style, 86.
 Ibid., 87.
 On certain happy occasions, what originated as spatially-oriented architectures transformed into placially-oriented architectures: I’m thinking of the exemplary cases of Frank Lloyd Wright or, decades later, Alvar Aalto, above all.
 Ibid., 57.
 Ibid., 64.
 Ibid., 85.
 Ibid., 77.
 In the book The Four Elements of Architecture, 1851, Gottfried Semper describes four basic elements from which architecture emerged: the hearth, the roof, the enclosure and the embankment. See Architectural Theory: From the Renaissance to the Present (Taschen, Bibliotheca Universalis, 2016), 434.
 The International Style, 40. ‘A FIRST PRINCIPLE: ARCHITECTURE AS VOLUME’ is the title of Chapter Four, where the first of the three principles of the new international style in architecture is introduced to the reader.
 Ibid., 249.
 I have also briefly talked about that in the note  of the article The 3rd Skin.
 Ibid., 20.
 Ibid., 24.
 Ibid., 66.
 Ibid., 68.
 Ibid., x.
 Ibid., 48.
 Ibid., 247 — Appendix to the 1966 edition, by Henry-Russell Hitchcock (1951).
 Modern Architecture – International Exhibition, Hitchcock and Johnson eds.New York: The Museum of Modern Art, 1932.
 See the pamphlet Built to Live In, by Philip Johnson,1931.
 Le Corbusier, Towards a New Architecture, (New York: Dover Publications, Inc., 1986) xix, 2. We have to point out that, at the date of the original French publication (1923), Le Corbusier was already conscious of the value of space as an important architectural tool; it is just that space was not the only element or the most important element, in his architectural considerations. His position is more complex (and complete I would say) given that traditional plastic values are complemented by the newly discovered spatial value; so, in Le Corbusier, traditional material elements and concepts like ‘mass’, ‘surface’ or ‘plan’ are complemented by the more recent concept ‘space’ to reach for a new aesthetical value, specific to modern architecture. That’s why in that book he commenced saying that ‘Architecture is a plastic thing’ (page 4), but he soon added that ‘The elements of architecture are light and shade, walls and space’ (page 5) hypothesizing an interpenetration of polar opposites, which has its theoretical foundation in the discussions about the essence of architecture (Is it the plan? Mass? Volume? Space?) that emerged in Europe in the second part of the XIX century.
 The International Style, 62.
 Ibid., 48.
 Ibid., 31.
 Ibid., 33.
 Ibid., 45.
 Ibid., 46-7.
 Ibid., 44.
 Ibid., 50.
 Ibid., 76.
 Ibid., 86.
 Ibid., 41.
 Ibid., 43, 44, 45, 48 (2), 49, 50, 56, 58 (2), 70, 71, 82. In the catalogue prepared for the exhibition, Modern Architecture: International Exhibition, the only (similar) reference to this terminology (surface of volume) is only traceable to the expression ‘immaculately surfaced volume’, page 94.
 Ibid., 41.
 Ibid., 41.
 Ibid., 86.
 Ibid., 87.
 Ibid., 246 — Appendix to the 1966 edition, by Henry-Russell Hitchcock (1951).
 Ibid., 26.
 Ibid., 30.
 Ibid., ix, 57, 101, 120, 126, 190, 206, 212, 255, 77, 204, 246.
 Ibid., 72, 76, 66, 93, 57, 86, 87, 88, 90, 203, 215.
 Ibid., 183.
 Ibid., 190.
 Ibid., 244.
 I omit those sentences containing the term ‘openness’ or the attribute ‘open’ we have already considered in the past sections.
 Ibid., 25.
 Ibid., 31.
 Ibid., 33.
 Ibid., 41.
 Ibid., 86.
 Ibid., 119.
 Ibid., 250.
 Modern Architecture: International Exhibition, eds. H-R. Hitchcock and P. Johnson (New York: The Plandome Press, 1932). The catalogue was printed in five thousand copies for the architectural exhibition held at the MoMA, New York, from February 10 to March 23, 1932.
 The International Style, vii, ix.
 See Part three – Ideas of space in German architectural theory 1850-1930, in Cornelis van de Ven, Space in Architecture (Assen: Van Gorcum, 1978).
 Modern Architecture: International Exhibition ,114.
 Ibid., 115.
 Ibid., 116.
 Ibid., 117.
 Ibid., 117-118.
 The structure of the present brief Appendix is based on two main sources: Cornelis van de Ven’s Space in Architecture (1978), and Adrian Forty’s entry ‘Space’, included in the book Words and Buildings: A Vocabulary of Modern Architecture (2000). Architecture understood, explained and taught as a science (of space) was an achievement of the Bauhaus school, under the guide of Walter Gropius especially.
 G.W.F. Hegel, The Philosophy of Fine Art, Volume III (London: George Bell & Sons, 1920), 93.
 See note 26 in Mitchell W. Schwarzer, The Emergence of Architectural Space: August Schmarsow’s theory of Raumgestaltung, in Assemblage, No 15 (Aug. 1991), 59.
 Concerning Semper’s concept of ‘movement in depth’ see van de Ven’s Space in Architecture, 77; concerning Semper’s notion of ‘enclosure’ as a basic element for architecture — a notion elaborated in the book The Four Elements of Architecture (1851) —see Architectural Theory: From the Renaissance to the Present (Taschen, Bibliotheca Universalis, 2016), 434.
 Adrian Forty, Words and Buildings: A Vocabulary of Modern Architecture (London: Thames & Hudson Ltd., 2000), 258. See also Van de Ven’s Space in Architcture (page 109) for a brief recognition of Sitte’s attention to the physiology of space perception.
 in, August Schmarsow, “The Essence of Architectural Creation”, in Empathy, Form and Space: Problems in German Aesthetics, 1873 – 1893, introduction and translation by H. F. Mallgrave and E. Ikonomou (Santa Monica: The Getty Center for the History of Art and the Humanities, University of Chicago Press,1993), 286, 287.
 Hendrik Petrus Berlage, Thoughts on Style 1886-1909, trans. by I. Boyd Whyte and W. de Wit (Santa Monica: The Getty Center for the History of Art and the Humanities, 1996), 29.
 Kenneth Frampton, Storia dell’Architettura Moderna (Bologna: Zanichelli Editore, 1993), 185.
 Concerning the different artistic movements that contributed to shape the idea of space in the first decades of the 20th century see Cornelis van de Ven’s Space in Architecture – Part Four: Ideas of space in the modern movements 1890-1930.
 David Gebhard, Schindler (London: Thames and Hudson, 1971), 191.
 Geoffrey Scott, The Architecture of Humanism, A Study in the History of Taste (New York: Houghton Mifflin Company,1914), 226.
 Sigfried Giedion, Space, Time and Architecture: The Growth of a New Tradition, fifth edition. Cambridge: Harvard University Press, 1967.
 in Nikolaus Pevsner, An Outline of European Architecture (London: Penguin Books, 1948), xix.
 Bruno Zevi, Architecture as Space: How to Look at Architecture, (1964), 22, 23.
Architectural Theory: From the Renaissance to the Present. Taschen, Bibliotheca Universalis, 2016.
Crutzen, Paul J. “The Anthropocene“. In Earth System Science in the Anthropocene, edited by Ehlers and Krafft. New York: Springer, 2006.
Forty, Adrian. Words and Buildings: A Vocabulary of Modern Architecture. London: Thames & Hudson Ltd., 2000.
Frampton, Kenneth. Storia dell’Architettura Moderna. Bologna: Zanichelli Editore, 1993.
Gebhard, David. Schindler. London: Thames and Hudson, 1971.
Giedion, Sigfried. Space, Time and Architecture, fifth edition. Cambridge: Harvard University Press, 1967.
Hitchcock, Henry-Russell and Johnson, Philip. The International Style. New York: The Norton Library, 1966.
—. Modern Architecture: International Exhibition. New York: The Museum of Modern Art, 1932.
Johnson, Philip. Built to Live In. New York: The Museum of Modern Art, 1931.
Le Corbusier. Towards a New Architecture. New York: Dover Publications, Inc., 1986.
Pevsner, Nikolaus. An Outline of European Architecture (London: Penguin Books, 1948.
Schmarsow,August. “The Essence of Architectural Creation” in Empathy, Form and Space: Problems in German Aesthetics, 1873–1893, introduction and translation by H. F. Mallgrave and E. Ikonomou. Santa Monica: The Getty Center for the History of Art and the Humanities, University of Chicago Press,1993.
Schwarzer, Mitchell W. “The Emergence of Architectural Space: August Schmarsow’s Theory of Raumgestaltung”, in Assemblage, No 15 (Aug. 1991), 48-61.
Scott, Geoffrey. The Architecture of Humanism, A Study in the History of Taste. New York: Houghton Mifflin Company, 1914
van de Ven, Cornelis. Space in Architecture. Assen: Van Gorcum, 1978.
Zevi, Bruno. Architecture as Space: How to Look at Architecture. New York: Horizon Press, 1964.
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