The main purpose of Cicero while at Athens had been to learn philosophy; in Asia and at Rhodes he devoted himself chiefly to rhetoric, under the guidance of the most noted Greek teachers, chief of whom, was his old friend Molo, the coryphaeus of the Rhodian school[29].  Cicero, however, formed while at Rhodes one friendship which largely influenced his views of philosophy, that with Posidonius the pupil of Panaetius, the most famous Stoic of the age.  To him Cicero makes reference in his works oftener than to any other instructor.  He speaks of him as the greatest of the Stoics[30]; as a most notable philosopher, to visit whom Pompey, in the midst of his eastern campaigns, put himself to much trouble[31]; as a minute inquirer[32].  He is scarcely ever mentioned without some expression of affection, and Cicero tells us that he read his works more than those of any other author[33].  Posidonius was at a later time resident at Rome, and stayed in Cicero’s house.  Hecato the Rhodian, another pupil of Panaetius, may have been at Rhodes at this time.  Mnesarchus and Dardanus, also hearers of Panaetius, belonged to an earlier time, and although Cicero was well acquainted with the works of the former, he does not seem to have known either personally.

From the year 77 to the year 68 B.C., when the series of letters begins, Cicero was doubtless too busily engaged with legal and political affairs to spend much time in systematic study.  That his oratory owed much to philosophy from the first he repeatedly insists; and we know from his letters that it was his later practice to refresh his style by much study of the Greek writers, and especially the philosophers.  During the period then, about which we have little or no information, we may believe that he kept up his old knowledge by converse with his many Roman friends who had a bent towards philosophy, as well as with the Greeks who from time to time came to Rome and frequented the houses of the Optimates; to this he added such reading as his leisure would allow.  The letters contained in the first book of those addressed to Atticus, which range over the years 68—­62 B.C., afford many proofs of the abiding strength of his passion for literary employment.  In the earlier part of this time we find him entreating Atticus to let him have a library which was then for sale; expressing at the same time in the strongest language his loathing for public affairs, and his love for books, to which he looks as the support of his old age[34].  In the midst of his busiest political occupations, when he was working his hardest for the consulship, his heart was given to the adornment of his Tusculan villa in a way suited to his literary and philosophic tastes.  This may be taken as a specimen of his spirit throughout his life.  He was before all things a man of letters; compared with literature, politics and oratory held quite a secondary place in his affections.  Public business employed his intellect, but never his heart.