(I've now reread the important chapter 11, and so will append my notes, in case they should prove useful to anyone -- apologies in advance for whatever typos/errors there are -- I don't have the patience to proofread most of the time...)
First let me say this is an excellent book - probably the best I've read so far on the topic. In addition to a detailed introduction (chs. 1-2), and an illuminating conclusion (chs. 11-12), the book contains detailed studies of the personalities and art of Henri Rousseau (1844-1910); Erik Satie (1866-1925); Alfred Jarry (1873-1907); Guillaume Apollinaire (1880-1918).
The critical chapter is chapter 11. What follows are simple notes (poorly digested, or at least carelessly thrown together -- so please excuse) from a quick reread of the chapter.
There are two keys, Shattuck thinks, to modernism -- in a formal or technical sense.
First (pp. 326-331), the 19th cen. began with a “spiritual revival”, as man began to search for the divinity within himself. The form of a work of art can imply this inward direction, as the work itself becomes the means or locus of the search. 20th cen. art has thus tended to search itself rather than exterior reality for the beauty of meaning or truth, a condition that entails relationships between author, audience, work, and world.
If all knowledge is subjective (as modern epistemologies suggests: Bergson/Coleridge), then art may come to embody its own reality (and its own infinity). It needs no external world, and indeed replaces the external world as an object of attention. Thus, literature and painting in the 20th cen. cease to be representational (or imitative) of external reality, and become instead self-sufficient creations rivaling reality.
The result is that art becomes self-reflexive and narcissistic – focusing on itself, the creative act, rather than on the world. As Alfred Jarry wrote: “Being, once rid of Berkeley’s burden, consists… not in perceiving or in being perceived, but in the iridescent mental kaleidoscope that thinks itself and of itself” (Mallarmé’s 'Ma pensée se pense'). Stendhal: “I ceaselessly ruminate on what interests me; by dint of regarding it in different positions of mind (âme), I end up seeing something new in it”. Thus, as early as Stendhal, the subject of a work is beginning to dwindle in importance before the carefully watched positions d’âme, which transform it into art. This process of transformation (for Stendhal, crystallization followed by disenchantment; for cubism, a methodical dissolution of material objects, a dissociation of visual ideas) carries all before it. The subject of a painting is not then what it started with, but what it ends up with. (Juan Gris: “To paint is to foresee what is going on in the whole composition of the painting when a certain form or color is introduced.”). Thus, artistic consciousness shrinks from the world into its own, mirrored realm.
The second key point that Shattuck makes (331ff.) concerns parataxis and hypotaxis. It is well known that archaic writers (and, in fact, this is one of the keys to archaic art generally) write paratactically. In Homeric Greek, for example, there are no subordinate conjunctions – what in later attic develop into subordinate conjunctions are simply adverbs in Homer – and so ideas and clauses and indeed, whole sections and ‘chapters’ are simply juxtaposed to one another, without any indication of the logical relations that are in play, and which the reader has to divine or intuit. If you can grasp this essential difference, then finally you will be well on your way to grasping archaic literature. The development of hypotaxis, in Greek, corresponds to the development of a huge suite – an extraordinarly large suite in Greek, as it happens – of the grammatical tricks of subordination (and hence of the subjunctive and of the use of the optative mood in subordinate clauses), which allow writers to specify with great precision precisely what are the logical relations between ideas. In philosophy, it is what allows for the development of logic, rhetoric, and advanced philosophy in Plato and Aristotle; and in literature for the structural properties of plot used by classical authors (5th cen. and later) and described by Aristotle in the poetics as the subordination of the parts to the whole in the unity of plot or mythos.
This same pattern repeats itself, by the way, in the move from early Medieval and Renaissance art to the classical art and literature in the West – starting probably with the Quattrocento in painting (perspectival painting), at least.
What Shattuck points out -- and this is the central point -- is that one of the keys to understanding modernism is precisely that the unity of classical composition (what he calls ‘transition’) breaks down again – and we return to parataxis, which he calls 'juxtaposition' (331ff.).
This compares with what William Barrett refers to (Irrational Man, 42-65) as the second of the three great “flattenings” that he identifies as being key to understanding modernism: the flattening of planes; the flattening of climaxes (with explicit reference to this problem in Aristotle); and the flattening of values. In the “flattening of climax”, the Aristotelian (classical) idea of beginning, climax, and denouement (in which the parts are subordinated structurally to the climax or to the central theme are flattened out – and everything, all the parts…, not unlike in Homer, gets its own value and spins off in its own direction. Think cubism).
The result is discontinuity – in style: surprise (Apollinaire’s word), illogicality, abruptness… obscurity; and, philosophically… Shattuck writes (338)…. the “absurd”, this “sense of life-without-links in ‘the discontinuousness of his chopped-up sentences’”, quoting Sartre’s appraisal of Camus narrative style. (Sartre, commenting on the “white” style of Camus’ L’étranger, writes: “But what is the postulate implied by this kind of narrative? It amounts to this, that out of what used to be melodic organization has been made a simple addition of invariable elements; the succession of mere movements is asserted as rigorously identical with the act in its totality…because he slyly filters out all significant connectives…”