To understand the philosophical ambitions of Broom it is worth first looking in detail at what Wallace thought Markson had done. Markson's novel, a work of experimental fiction with a lean style reminiscent of Samuel Beckett, is narrated by a painter named Kate, who appears to be the last person alive and who has been alone on earth for many years by the time the novel opens. Kate doesn't so much narrate (for she has no audience) as write into the void, tapping out on a typewriter declarative statement after declarative statement in simple paragraphs of just one or two sentences. Unlike many novels of ideas, Wittgenstein's Mistress doesn't feature cerebral characters or lofty discussions. Though Kate makes highbrow allusions, her grasp of history and literature and philosophy is idiosyncratic and shaky. As Wallace noted, in Kate's hands intellectual ideas are "sprayed, skewed, all over the book."
After many years roaming the earth, futilely looking for anyone else, Kate has retired to a beach house, where she is writing out her thoughts. She does so with a peculiar controlled indirection, free-associating but looping back again and again to a recurring set of personal preoccupations—compulsively trying to keep straight the memory of what has been lost, organizing and reorganizing scattered memories of her own life and her piecemeal knowledge of the world to which she once belonged:
I do remember sitting one morning in an automobile with a right-hand drive and watching Stratford-on-Avon fill up with snow, which must surely be rare.
Well, and once that same winter being almost hit by a car with nobody driving it, which came rolling down a hill near Hampstead Heath.
There was an explanation for the car coming down the hill with nobody driving it.
The explanation having been the hill, obviously.
That car, too, had a right-hand drive. Although perhaps that is not especially relevant to anything.
The possibility increases that Kate's narration is unreliable, that she is mentally unhinged, as it becomes clearer that the onset of her peculiar experience of the world coincided with a profound personal loss. The book imparts a double-layered feeling of loneliness and isolation: Kate's is the voice of a writer trapped not only inside her own head but also inside a world that now exists only through her own continual reconstructing of it. The text she types, Wallace wrote, "is itself obsessed & almost defined by the possibility that it does not exist, that Kate does not exist."
What does any of this have to do with Wittgenstein? Part of the achievement of Markson's novel, one of the ways in which it avoids the pitfalls of many novels of ideas, is that it doesn't require any understanding of Wittgenstein. The novel operates on its own terms. But the allusion to Wittgenstein in its title, its repeated citation of the first sentence of the Tractatus ("The world is all that is the case"), and its stylistic affinity with that book (the Tractatus is also composed of short aphoristic paragraphs) all invite the reader versed in philosophy to wonder what Markson is up to. "This isn't a weakness of the novel," Wallace stressed. "Though it's kind of miraculous that it's not."
Wallace had read the Tractatus, of course (he wrote to Lance Olsen that he thought its first sentence was "the most beautiful opening line in western lit"). He knew that Wittgenstein's book presented a spare and unforgiving picture of the relations among logic, language, and the physical world. He knew that the puzzles solved and raised by the book were influential, debatable, and rich in their implications. But as a flesh-and-blood reader with human feelings, he also knew, though he had never articulated it out loud, that as you labored to understand the Tractatus, its cold, formal, logical picture of the world could make you feel strange, lonely, awestruck, lost, frightened—a range of moods not unlike those undergone by Kate herself. The similarities were not accidental. Markson's novel, as Wallace put it, was like a 240-page answer to the question, "What if somebody really had to live in a Tractatusized world?" Pronouncing the novel "a kind of philosophical sci-fi," Wallace explained that Markson had staged a human drama on an alien intellectual planet, and in so doing he had "fleshed the abstract sketches of Wittgenstein's doctrine into the concrete theater of human loneliness."