The growing body of scholarship on Swedish artist Hilma af Klint reveals ever more about the remarkable collection of paintings she created in the early years of the twentieth century, many of which stand as powerful examples of abstract painting. From the time of the 1986 exhibition The Spiritual in Art: Abstract Painting 1890–1985 through multiple, more recent, retrospectives, she has been mentioned side­ by­ side with the better­ known exemplars of abstraction: Wassily Kandinsky; Piet Mondrian; Kazimir Malevich; and Frantisek Kupka. However, how to understand af Klint’s urge to abstraction in relation to theirs has been something of a mystery, since, working in Stockholm, she was not a part of avant garde artistic networks in this period. All of these artists shared a commitment to painting as a revelatory practice. More importantly, however, they also shared something more fundamental which has not been recognised in most histories of modern art. These were the interna­tional cultures of science and occultism that served as a substructure for the develop­ment of modernism across Europe. And central to the information travelling on these networks was a leitmotif of the period, critical for many modern artists — the existence of invisible realities beyond the reach of the human eye.

With discoveries in the 1890s such as X­-rays, radioactivity, and the electron, sci­ence in the later nineteenth century had dramatically undercut the visible world as the appropriate focus for artists or seekers of a truer understanding of the nature of reality. Occultists, including both spiritualists and theosophists – movements in which af Klint was deeply engaged– regularly drew upon such discoveries, which gave new purchase to arguments previously grounded largely in idealist philoso­phies or occult and mystical traditions. If French symbolism has been seen as the crucial background for avant garde artists’ development of abstraction, the very idea of correspondences, as promulgated by the poet Charles Baudelaire, was derived from the writings of Swedish scientist and mystic Emanuel Swedenborg who had posited such a direct connection between this world and a higher reality. Swedenborg’s ideas were well known in Swedish culture, and af Klint’s sense of a language that had once been known and was now lost was a basic Swedenborgian tenet. The Swedish writer had also had a significant impact upon spiritualism, as well as on Rudolf Steiner, who played a key role in af Klint’s development of ideas. Swedenborg was likewise a source for the highly influential German mystic philosopher Carl du Prel, two of whose books were in af Klint’s extensive library. Du Prel, to whom we shall return, was also a key inspiration for the internationally oriented spiritualist journal Die uebersinnliche Welt [The Supernatural World]. Published monthly in Berlin from 1896 to 1922, the journal is a testament to the robustness of spiritualism during the period in which af Klint engaged with the movement, from the 1890s through the first decade of the century.

This essay focuses on two themes from the early twentieth century af Klint explored in her painting – the ether, and the fourth dimension – both of which served as signs of the invisible meta­realities that figured importantly for the other pioneers of abstraction. Typically of this period, when science and the occult were not strictly demarcated and when such ideas travelled so internationally, the ether and the fourth dimension appear in a wide variety of popular scientific and mathematical sources, as well as in the writings of figures such as du Prel and the theosophists Steiner, C. W. Leadbeater, and Claude Bragdon. Af Klint joined the Swedish Lodge of the Theosophical Society in 1889 and encountered Steiner’s writings and lectures in the context of theosophy, before he founded the Anthroposophical Society in 1913. Bragdon’s A Primer of Higher Space (The Fourth Dimension) of 1913 and Four-Dimensional Vistas of 1916 cite du Prel and Swedenborg, attesting to the inter­national currency of their ideas. Bragdon distributed copies of his books widely on theosophical networks, from Theosophical Society offices and journals to individu­als such as Steiner and Leadbeater.

The two books by Carl du Prel that af Klint owned in Swedish translation were Die Philosophie der Mystik [The Philosophy of Mysticism] (1885) and Die Monistische Seelenlehre: Ein Beitrag zu Lösung des Menschenrätsels [The Monistic Doctrine of the Soul: A Contribution to the Solution of the Riddle of Man] (1888), which she anno­tated. Du Prel’s books were translated into at least five languages, making him an internationally known author to whom af Klint was closely attuned. And his writings provide critical context for her belief in a spirit world or transcendent realm beyond ordinary experience with which she could communicate.

Well before the discovery of the X­-ray in 1895 undercut confidence in the human eye, du Prel argued against materialism and dualism and for the existence of a transcendent realm that could be accessed by a ‘transcendental Subject’ not con­tained in the self-­conscious ego. His ‘monistic doctrine of the Soul’ signified a continuum between matter and spirit with a movable ‘threshold of sensibility’ by which an individual in a somnambulistic state could access higher realms. Du Prel connected his moving threshold to Darwinian evolution and foresaw future states of higher consciousness as well as ‘biological exaltation’—an argument Madame Helena Blavatsky, theosophy’s founder, would make as well. Du Prel’s philosophy surely underlies af Klint’s lifelong commitment to overcoming duality and achiev­ing harmonious unity in her works.

Af Klint and her spiritualist circle, The Five, who, from 1896, worked together for about ten years, were thus part of a cultural orientation in the late nineteenth century that, in the tradition of Swedenborg, considered interaction between visible and invisible worlds as a natural possibility. One of the members of The Five, Mathilde Nilsson, published a spiritualist journal, and, on the model of Die uebersinnliche Welt, it would have been following the latest developments in science that now added evidence for the spiritualist cause. Initially, af Klint and her friends made mediumistic drawings, and her initial response to the 1906 request from one of their ‘High Masters,’ Amaliel, that she create a large series of ‘Paintings for the Temple’ was to work directly under his guidance. Af Klint later wrote of her ‘sensi­tivity to mediumistic currents while executing occult drawings’, and a message received by one of The Five in February 1905 reflected just such a contemporary con­ception of vibrating waves: ‘Be careful with your drawings, they are images of bath­ing [encompassing] ether waves that are awaiting you when your ears and eyes can experience messages.’ When af Klint resumed work on the commission after a hia­tus from 1908 to 1912, she described working with greater creative control. Although we cannot know how af Klint was actually operating in her artistic practice, du Prel’s argument that a subject’s threshold of sensibility could be moved not only by somnambulism but by ‘a high tension of imaginative power’ would certainly have encouraged af Klint’s visionary pursuits. Du Prel also marshalled evidence from science to support his arguments, including both ether vibrations and the new speculation on a spatial fourth dimension. These two concepts would continue as prominent cultural themes in the wake of the new scientific discoveries of the 1890s, and would come to play major roles in theosophical doctrine as well as in spiritualism. Early twentieth­ century artists as well as theosophists and spiritualists, however, could never have imagined the way in which cultural developments during the later 1910s and subsequent decades would obscure their shared interests in the ether and higher dimensional space. Yet the popularisation of Einstein’s relativity theory beginning in late 1919 would severely undercut both of these ideas. In the wake of an eclipse expedition’s confirmation of one of the postulates of the 1915 general theory of relativity, ‘science’ was transformed into an abstract mathematical realm in which the fourth dimension was redefined as time (versus space) in a four­-dimensional ‘space­time continuum’. And the ether, so central to the cultural imagination for decades, was largely dismissed as irrelevant to physics. Beginning in the 1920s, relativity theory’s occluding of the ether physics that had dominated the public’s understanding of science during the first two decades of the century caused a startling shift for artists and others grounded in that paradigm, as well as a problem for later art historians and cultural historians more generally.

Instead of Einstein, the backdrop for the emergence of modern art, including the work of af Klint, was the succession of scientific discoveries and developments of the 1890s and early years of the new century noted earlier. The X­-rays discovered by Wilhelm Röntgen in 1895 made solid matter transparent and emphatically estab­lished the inadequacy of the human eye as a perceiving instrument. Wireless telegraphy’s development in the later 1890s, based on Heinrich Hertz’s 1888 confir­mation of the existence of electromagnetic waves, focused public attention on a vibratory, space­-filling ether, which went beyond simply the ‘luminiferous ether’ of the wave theory of light of the 1820s. Posited by scientists as necessary for the transmission of wave vibrations, the impalpable ether was understood to fill all space and to interpenetrate all matter; by the end of the century it was being assigned numerous other functions as well. Beyond the X­-ray’s actual breaching of material surfaces, confidence in the solidity of matter had been further challenged by Henri Becquerel’s 1896 discovery of radioactivity, J. J. Thomson’s 1897 detection of the electron, and the Curies’ identification of the first radioactive elements in 1898. Research on the atom and its structure by Ernest Rutherford, the Curies, and others kept the atom at the forefront of popular scientific news through the pre­ World War I years.

In this period it was often suggested that all matter might be radioactive, offering a new view of objects as endlessly emitting particles into the surrounding ether, an idea popularised in the best­selling books of Gustave Le Bon, such as L’Evolution de la matière [The Evolution of Matter] of 1905. At the same time, physicists such as Sir Oliver Lodge, building on Lord Kelvin’s concept of the ‘vortex atom’, proposed the ‘electric theory of matter’, in which matter was thought to be born through the interaction of the electron and the ether, an idea to which both Kandinsky and the futurist Umberto Boccioni responded in their writings. Lodge was probably the scientist best known to the public in the years before World War I: he wrote exten­sively in popular journals and, because of his openness to spiritualism and psychical research, he was followed closely by both spiritualists and theosophists. It is thus not surprising to find af Klint making a set of watercolour paintings titled Ether Convolute as part of her 1916 Parsifal Series, in which convolution suggests the formation of matter from amorphous fields of colour. Likewise, af Klint turned her attention to the atom in her 1917 Atom Series, in which she juxtaposed diagrammatic images of the atom on the etheric plane and on the physical plane with added annotations such as: ‘When the atom expands on the etheric plane, the physical part of the earthly atom begins to glow’.

Yet af Klint’s usage of ‘etheric plane’ documents that she was not only referring to physics but also to theosophy, where the etheric or ether plane figured as an inter­ mediate step between the physical plane and the astral and mental planes. As Leadbeater and Annie Besant explained in the introduction to their 1905 book Thought-Forms, ‘As knowledge increases, the attitude of science towards the things of the invisible world is undergoing considerable modification … Ether is now comfortably settled in the scientific kingdom [and] … Roentgen’s rays have re­arranged some of the older ideas of matter, while radioactivity has revolutionised them, and is leading science beyond the borderland of the ether into the astral world.’ Blavatsky discussed the ether and its long history in occultism in both Isis Unveiled (1877) and the book af Klint owned, The Secret Doctrine (1888). Besant and Leadbeater’s 1908 Occult Chemistry, to which af Klint’s Atom Series has been compared, concluded with an appendix on ‘The Aether of Space’, which quoted extensively from Lodge’s writings.

Like the ether (and the X­ray), the fourth dimension was another site where science (or mathematics in this case) and theosophy readily intersected. Indeed, the fourth dimension became a major element in the discourses of both Leadbeater and Steiner, serving the former as a means to discuss the astral plane and astral vision – and for the latter as a central vehicle in his lectures to introduce the concept of higher consciousness. The idea of a suprasensible fourth dimension of space had grown out of the development of n-dimensional geometries in the mid­-nineteenth century. If space actually possessed an additional dimension, our familiar three­-dimensional world would then be merely a section or shadow of a higher, imperceptible reality – an idea supported from its earliest days by invocations of Plato’s allegory of the cave. A plate from Bragdon’s Primer of Higher Space clarifies the relationship of successive dimensions and how they could be conceived as folded down in a lower space. Artists in nearly every modern movement responded to the fourth dimension in its various guises during the early years of the twentieth century and beyond. Today, extra spatial dimensions figure prominently in string theory in physics.

Leipzig astronomer J. C. F. Zöllner had been one of the first advocates of the idea of a spatial fourth dimension, which he adopted to explain the activities of spirit medium Henry Slade in the 1870s. Zöllner’s writings, including his volume Transcendental Physics, provided support for du Prel’s arguments, and the fourth dimen­sion would continue to be associated with spiritualism in the following decades. The most influential populariser of the spatial fourth dimension was the English­ man Charles Howard Hinton, who presented the first systematic discussion of the concept and its idealist philosophical implications in his books A New Era of Thought (1888) and The Fourth Dimension (1904). Hinton was a primary source of information on the fourth dimension for the theosophists Leadbeater, Steiner, Bragdon, and P. D. Ouspensky in Russia (a vital stimulus for Malevich), and these figures all helped to spread Hinton’s ideas widely. In his books Hinton argued that the Kantian ‘space sense’ could be educated and enlarged to perceive a fourth spatial dimension through focused study of the spatial arrangement of forms – in this case a complex system of multicoloured cubes representing sections of the four­-dimensional hyper­ cube or tesseract. Hinton was far from a mystic, and his approach to enlarging consciousness was a highly pragmatic one, a stance especially appreciated by Steiner. Leadbeater had discovered Hinton’s writings by the time he published Clairvoyance in 1899, a text in which he responded to both the discovery of the X­ray and its ability to ‘see’ through matter, and the analogous notion of a fourth dimension that would open up three-dimensional forms to higher dimensional vision. In Clairvoyance Leadbeater argues that Blavatsky’s lack of enthusiasm for the concept of the fourth dimension was because she was thinking of it only in terms of this X­ray like, see­-through vision, which he associated with the level of ‘etheric vision’ – below true astral vision. This was the marvel of the fourth dimension for Leadbeater – that it could explain not just the seeing­-through of etheric vision, but also the higher level of knowledge he associated with the astral plane. In astral vision objects would be seen from all sides at once ‘and every particle of the inside’ would be visible as well. The astral world and plane were central concepts for af Klint: she refers to them repeatedly in her writings. Indeed, in Group II of the Parsifal Series in the two sets of watercolours titled Physical Plane Convolute and Astral Forces Convolute af Klint’s directional notations added to her monochromatic squares suggest an analogue to Leadbeater’s multidimensional astral vision: ‘forward’, ‘backward’, ‘downward’, ‘upward’, ‘outward’ and ‘inward’, with the ‘backward’ [bakåt] written in reverse.

Like Leadbeater, Steiner was a great admirer of Hinton. In his lectures all over Europe beginning in 1905 he introduced his audiences to the geometrical ideas of the ‘wise man Hinton’. Although Steiner never published on the fourth dimension during his lifetime, notes taken on his lectures and their illustrations appeared in a 1995 publication. Af Klint heard Steiner lecture in Stockholm in 1908 and met him then; she heard him lecture again in 1912. As Steiner explained at the start of the third lecture of a series in Berlin in 1905: ‘As you know, the reason we tried to envi­sion the possibility of four­-dimensional space was to gain at least some idea of the so­ called astral realm and still higher forms of existence.’ For Steiner, learning to conceive four­-dimensional objects was a means to prepare students for ‘the very different nature of the objects and beings that we encounter in the so­ called astral world’.

Two of Af Klint’s paintings from The Tree of Knowledge group (No. 3 and No. 4) of 1915 demonstrate her commitment to theosophy’s successively higher planes of existence: she specifically labels the levels of ‘ether plane’, ‘astral plane’, and ‘mental plane’. As Leadbeater had explained in his 1902 An Outline of Theosophy in his chapter The Constitution of Man:

To these inner worlds or different levels of nature we usually give the name of planes. We speak of the visible world as ‘the physical plane’, though under that name we include also the gases and various grades of ether. To the next stage of materiality the name ‘the astral plane’ was given by the medieval alchemists . . . and we have adopted their title. Within this exists yet another world of still finer matter, of which we speak as ‘the mental plane’, because of its matter is composed of what is commonly called the mind in man.

Higher dimensions gave Leadbeater and theosophists like af Klint a means to under­ stand the interconnection of the various planes of existence – physical (with its ether component), astral, mental – as not like separate shelves in a bookcase, but rather as completely interpenetrating.

Similarly, the widespread belief in the ether as filled with vibrating waves and interacting with matter offered a model not only for a continuum of matter and ether but also for the unity of matter and spirit.

Contemporary ether physics thus provided a useful backdrop for theosophists such as Leadbeater and Steiner to explain their doctrines to the public. As Leadbeater wrote in Man Visible and Invisible in 1902, ‘It is universally recognised that ether penetrates all known substances, the densest solid as well as the most rarefied gas; and just as it moves with perfect freedom between the particles of the denser matter, so does astral matter interpenetrate it, in turn, and move with perfect freedom among its particles.’ From her copy of Steiner’s 1908 Theosophy, af Klint would also have been aware of his further clarification of the ‘ether­body’, which he differenti­ated more specifically from the physical body as the ‘life­body’ or ‘the life within the physical body’. For Steiner it was the ether­body/life­body that formed the transi­tion to the ‘sentient ­soul’ of an individual, as he explained: ‘a portion of the ether­ body is finer than the rest, and this finer part of the ether­body forms a unity with the SENTIENT­ SOUL, while the coarser part forms a kind of unity with the phys­ical body’. Af Klint’s reading of Steiner would have complemented her grounding in du Prel’s monistic rejection of the duality of matter and spirit, a theme she had signified in the first phase of her Paintings for the Temple by prevalent letters u (spirit) and w (matter). Finding new means to signify the overcoming of that duality to achieve unity would be central to the second phase of her Paintings for the Temple, particularly during 1915.

Much of af Klint’s art reflects the sense of evolutionary progress that underlay du Prel’s philosophy and theosophical doctrine, particularly the evolution of human consciousness to successively higher levels. Another site where such evolutionary thinking was prominent was the extensive literature on the spatial fourth dimen­sion, which, for its advocates, necessarily involved the development of new mental powers. Bragdon, for example, discussed du Prel’s ‘movable threshold of conscious­ness’ in the Primer of Higher Space. And this was what made Hinton’s cube system and his exercises for mental development so appealing to Steiner, encouraging him to incorporate the fourth dimension into his lectures. Given Steiner’s strong commitment to the subject and his inclusion of extensive geometrical diagrams in his lectures, the literature on the fourth dimension provides new insights into af Klint’s stylistic move toward geometry in the course of her second series of Paintings for the Temple, beginning in 1912, just as she encountered Steiner’s ideas again in his Stockholm lectures.

Aspects of af Klint’s earlier Paintings for the Temple – spirals as well as right­ and left­handed symmetry, along with evolution more generally – are also prominent themes in the early writing on the fourth dimension and would have prepared her well to make the transition to a geometric form language. The spiral was a central motif for af Klint in the context of her early mediumistic paintings, such as Primordial Chaos, No. 16 (1906–1907), just as the shell played an important role in many of her figurative Evolution paintings, as in the WUS Series of 1908. Right and left­ handed spiralling shells embodied for af Klint the duality of male (yellow) and female (blue) that she sought to overcome. While in Evolution, No. 4 the two shells are overlaid, in other works of the series, such as Evolution, No. 6, the yellow and blue shells are juxtaposed as mirror images.

Right­ and left­-handedness and related growth in nature – as in shells and plants – had figured in the earliest speculation on the possible existence of a higher dimen­sion of space. From the time of Möbius and Kant in the eighteenth century, it was clear that only in a fourth dimension could a right hand be turned into its mirror image, a left hand. Like other advocates of the fourth dimension, Bragdon set forth this case in his Primer of Higher Space, implying as well that when two symmetrical forms were made to coincide in the fourth dimension, their duality and opposition would be overcome by unity.

One of af Klint’s first specific visual responses to the fourth dimension was her adop­tion of the unfolded hypercube to create a kind of higher dimensional crucifixion image. In No. 5, Group VIII, The US Series an X­-ray­like transparent figure (presum­ably Christ) is flanked on a hypercubic cross by two figures perhaps representing other races or religions; below at left and right are a transparent male and female on conventional crosses, coded with af Klint’s standard yellow for male and blue for female. The X-­ray imagery suggests both Leadbeater’s conception of etheric vision and Bragdon’s illustration of ‘clairvoyant (4 ­dimensional vision)’ with an X­ray image in his Primer of Higher Space, which also included an unfolded hypercube encasing a figure on its frontispiece. Bragdon had sent Steiner a copy of his small 1912 book Man the Square: A Higher-Space Parable in January 1912, and the high­lighted black planes in af Klint’s image strongly suggest that she had seen Bragdon’s illustrations in the context of Steiner’s April 1912 lectures in Stockholm or through the Theosophical Society there. Although there were no hypercube images in Man the Square, it was a parable about a ‘Christos’ cube who was ‘crucified’ by folding himself down into a plane world. It is conceivable that af Klint encountered Bragdon’s Primer, since he shipped the first copies in November 1913; but she may also have synthesised this idea herself from hypercube drawings she had seen in Steiner’s lectures or other fourth dimension literature.

It was in af Klint’s 1915 series of paintings titled The Swan, however, that she responded most creatively to the fourth dimension. Here she moved beyond illustra­tion to explore a geometric form language grounded in Leadbeater’s identification of the astral plane with the fourth dimension. The new geometry thus offered af Klint an effective means to embody theosophical doctrine as well as her belief that male and female would come to coincide on the astral plane – this was what its four-­dimensionality would make possible. In the early stages of the series af Klint recast an initial image of a white swan (female/blue) above a black swan (male/ yellow) (The Swan, No. 1) into a contrast between concentric circles of cubic forms, with blue and yellow rays defining female above and male below (The Swan, No. 8). In her quest for ‘primordial images’, as she termed them, this was a distinct step away from the organic to geometric signs free of the associations of the visible world. However, the geometry here was still highly three­-dimensional, and if the Swan paintings were to truly signify the astral plane, then her geometry would need to be dematerialised and more suggestive of higher dimensions. In The Swan No. 9 that transformation begins to occur with cubes now rendered more transparently as well as axonometrically – akin to the projection technique used in both Steiner’s illustra­tions and in Bragdon’s Primer. This kind of see­-through view dematerialised the cube and began to suggest Leadbeater’s conception of astral vision – something that went beyond the simple transparency of etheric vision to a kind of seeing from all directions at once, the theme she would explore in her Group II of the Parsifal Series. This new approach is apparent in The Swan, No. 21 and The Swan, No. 23. In No. 21 the transparent cubic forms, once again coded as yellow and blue (male and female) seem to evolve out of more organic shapes. These are, in fact, spirals that, instead of opposing one another as in earlier works, are both right­-handed spirals, now inter­locking, suggesting the fusion of male and female af Klint believed would occur on the astral plane. That this new geometric form language became increasingly useful for af Klint is confirmed in No. 23 of the series, where she effectively suggests three levels of existence, as she had done in the Tree of Knowledge Series. Now the physical plane (with its ether element), the astral plane, and the mental plane are juxtaposed, with an increasing rarefication suggested by the move of the vivid hues of the spec­trum of visible light at the bottom toward the invisible spectrum above. It is as if white, ‘the colour of perfect faith’ for af Klint, creates pastels of infrared and ultra­ violet as well as of her symbolic colours of yellow and blue. Here, the biological language of her Tree of Knowledge, so rooted in early twentieth­ century form languages, is transformed into an image that transcends a specific moment.

Yet in her quest for universal imagery, af Klint was very much a part of her histor­ical context. Returning to The Swan, No. 9 and juxtaposing it with The Swan, No. 10, there is another motif that expressed her specific belief in ‘harmonious oneness’ and the overcoming of duality and chaos. Here, two images of chaos, tinged yellow and blue, are united by a vibration figure, akin to those discussed and illustrated by Besant and Leadbeater in Thought-Forms, but now bearing beads of spectral colour. Indeed, that same figure had been present in The Swan, No. 9. In addition, in the lower half of the image at the right is a tiny axonometric cube, uniting yellow and blue and suggesting the same emergence of geometry and order out of chaos that appears implicitly in The Swan, No. 9. Af Klint would continue during 1915 to pursue geometric forms and colour on their own, culminating in her remarkable, large­ scale Altarpieces. She had found a way to speak through pure geometry to convey her philosophical message of unity and existence on higher planes. In the Altarpieces, circles as signs of oneness become increasingly prevalent, along with triangles (both the Christian trinity and theosophical six­pointed stars) as well as echoes of earlier forms such as the highly resonant spiral in its right­ and left­-handed versions of blue and yellow.

In the late nineteenth and early twentieth century, in a world dominated by ether physics, public attention was directed much more so than today to the fact that the entire electromagnetic spectrum represented a oneness of nature, with wave phenomena (visible light and colour, X-­rays, Hertzian waves) distinguished only by their signalled continuity, vibrations exemplified another kind of harmony and unity. Embraced by occultists and scientists, ether vibrations – as well as popular interest in the spatial fourth dimension – offered Hilma af Klint new conceptual means to express her spiritual vision. She developed her unique abstract painting style working in Stockholm apart from the development of abstract painting else­ where, except for seeing works by Edvard Munch in 1894 and by Kandinsky in 1914. Yet, she was, in fact, grounded in the same international cultural substructures focused on invisible realities as Kandinsky, Mondrian, Malevich, and Kupka. Recov­ering this context of popular science and occultism, including theosophy, spiritual­ ism, and the writings of du Prel, offers vital new clues to aid a twenty­-first century viewer in understanding the paintings of this highly original visionary artist.

This essay originally appeared under the title Hilma af Klint and the Invisible in Her Occult and Scientific Context in Hilma af Klint: Visionary, Axess, 2019.