This dissertation focuses on those poetic quotations which Cicero employs both in his rhetorical and philosophical works and aims to identify the role of these citations and to determine his art of quotation. Poetry is an important component of his desire to make publicly available a Romanized version of Greek philosophical and rhetorical theories, a desire which supports his convictions that knowledge of this literary medium is an essential part of the orator's make-up and is a valuable tool of instruction and a source of learning for the philosopher. Previous studies of poetry in Cicero's works have neglected for the most part detailed analyses of his use of poetry in conjunction with that of his contemporaries - such analyses, however, are a necessary starting point if we want to acquire an informed picture of his art of quotation. Intertextual comparisons between his early rhetorical treatise de Inuentione and the Auctor's Rhetorica ad Herennium and between his 'mature' treatises and Varro's contemporaneous linguistic treatise de Lingua Latina and his near contemporaneous dialogue Res Rusticae not only establish several basic and advanced fundamentals of a Latin prose author's employment of poetic quotations, but also confirm that Cicero's art of quotation is more innovative, flexible, and vibrant than that of his contemporaries. In addition to Cicero's techniques of citation detailed intratextual examinations of his rhetorical treatise de Oratore and his philosophical treatise de Diuinatione reveal the often complex role poetry plays in the interaction between the interlocutors. The key to these two investigations is the interlocutors' practice to contest ownership of the same poetry by repetition or allusion. This struggle for poetic rights reflects the notion that poetry is public domain and, crucially, extends to the reader's reception of and involvement with the text. The examined evidence demonstrates that quotations are not only a malleable organizational tool for the formal structure of a treatise, but also constitute for the characters an important and emphatic means to support or refute key points, thereby helping to resolve the aporetic nature of the discourse.