IN early twentieth-century treatments of the novel’s evolution as a genre, Margaret Cavendish is mostly missing. When we do catch a glimpse of her, she makes her appearance as a literary critic rather than a contributing author in her own right. In the topic’s magnum opus, The Origins of the English Novel, 1600–1740, for instance, Michael McKeon places her in the company of Meric Casaubon and Père le Moyne, who are at pains to distinguish between historical accounts on the one hand and fictional romances on the other. Here, Cavendish insists that her Life of William—the biography of her husband released the year after her science romance, The Blazing World, was published—is historical and not to be confused with “pleasant Romances,” which amount to “telling Romansical Falshoods for Historical Truths.” Cavendish voices precisely the period’s urge to tease fact from fiction at a moment in time when “narrative” accounts of any sort seemed to be mixing the two modes, an urge ripe for careful scrutiny and therefore rightly at the heart of McKeon’s guiding premise. “To formulate the problem of the origins of the novel in terms of how one dominant prose form ‘became’ another,” he writes, “is really to ask how romance responded to the early modern historicist revolution. In seventeenth-century prose narrative, verisimilitude and the claim to historicity are incompatible and competitive expressions of that revolution.” Cavendish’s contemporary, Casaubon, insists on this fundamental incompatibility, for he is not convinced that “a thing is true, because it is possible; no, nor because probable: nay, it is certain that many lyes and falshoods are founded upon this very thing, probability.” The truth of history is anchored in certainty, not adrift in probability.