The Academic Questions, Treatise De Finibus and Tusculan Disputations, in English translation

According to Wikipedia: "Marcus Tullius Cicero (January 3, 106 BC – December 7, 43 BC) was a Roman philosopher, statesman, lawyer, political theorist, and Roman constitutionalist. Cicero is widely considered one of Rome's greatest orators and prose stylists. Cicero is generally perceived to be one of the most versatile minds of ancient Rome. He introduced the Romans to the chief schools of Greek philosophy and created a Latin philosophical vocabulary, distinguishing himself as a linguist, translator, and philosopher. An impressive orator and successful lawyer, Cicero probably thought his political career his most important achievement. Today, he is appreciated primarily for his humanism and philosophical and political writings. His voluminous correspondence, much of it addressed to his friend Atticus, has been especially influential, introducing the art of refined letter writing to European culture. Cornelius Nepos, the 1st-century BC biographer of Atticus, remarked that Cicero's letters contained such a wealth of detail "concerning the inclinations of leading men, the faults of the generals, and the revolutions in the government" that their reader had little need for a history of the period. During the chaotic latter half of the first century B.C. marked by civil wars and the dictatorship of Gaius Julius Caesar, Cicero championed a return to the traditional republican government. However, his career as a statesman was marked by inconsistencies and a tendency to shift his position in response to changes in the political climate. His indecision may be attributed to his sensitive and impressionable personality; he was prone to overreaction in the face of political and private change. "Would that he had been able to endure prosperity with greater self-control and adversity with more fortitude!" wrote C. Asinius Pollio, a contemporary Roman statesman and historian."