In my discussions of how aptitude operates in the composition theory of the United States, I explore current-traditional, expressivist, and social rhetorics. Although classical commonplaces persist, I argue that American rhetoricians, relying upon universal, Enlightenment conceptions of human nature, hope to make language training accessible to a wide range of human beings. These egalitarian attempts, however, reveal uncomfortable consequences. For example, the meritocratic possibilities of current-traditional rhetoric are challenged by static conceptions of language and mind---and, importantly, the rise of standardized language testing in the first quarter of the twentieth century. Also, expressivist rhetoric, exemplified by Peter Elbow's enthusiasm for the discovery of authentic voice, may lead to the construction of a false expression/rationality binary and the exoticizing of the texts and experiences of marginalized students. Finally, I describe how James Berlin and other social rhetoricians situate themselves in the current nativist debate led by cognitive psychologists, psychometricians, and conservative educators.

This dissertation interrogates how classical rhetoric and three broad formations of rhetoric in the United States have defined and deployed aptitude, a keyterm signifying the innate traits that impact the speaking and writing performances of students. Analyzing aptitude as an ideological construct, I argue that it plays important roles in determining the boundaries of rhetorical theory, forming judgments about the natures of individuals and human beings, and providing a "natural" means to justify the exclusion of certain groups (e.g., non-citizens, women, and other marginalized groups) from rhetorical training.

In my examination of classical rhetoric, I argue that statements about innate talents can be categorized according to their strength, that is, to how rigidly natural ability is conceived of as determining final linguistic performances. The strongest position maintains that innate differences in human nature determine linguistic performances and account for social stratification. A less restrictive version of aptitude, one advocated by Isocrates, Cicero, and Quintilian, maintains that though natural ability is important, gifted students still require training, practice, and experience if they are to become ideal orators. Finally, a sophistic position denies either the importance or existence of natural traits.