With the new arrangement, under which boys might become legally men at an earlier age than in the old days, it is obvious that there must often have been an interval before they were physically or mentally qualified for a profession.  As the sole civil profession to which boys of high family would aspire was that of the bar, a father would send his son during that interval to a distinguished advocate to be taken as a pupil.  Cicero himself was thus apprenticed to Mucius Scaevola the augur:  and in the same way the young Caelius, as soon as he had taken his toga virilis, was brought by his father to Cicero.  The relation between the youth and his preceptor was not unlike that of the contubernium in military life, in which the general to whom a lad was committed was supposed to be responsible for his welfare and conduct as well as for his education in the art of war:  thus Cicero says of Caelius[294] that at that period of his life no one ever saw him “except with his father or with me, or in the very well-conducted house of M. Crassus” (who shared with Cicero in the guardianship).  “Fuit assiduus mecum,” he says a little farther on.  This kind of pupilage was called the tirocinium fori, in which a lad should be pursuing his studies for the legal profession, and also his bodily exercises in the Campus Martius, so that he might be ready to serve in the army for the single campaign which was still desirable if not absolutely necessary.  When he had made his first speech in a court of law, he was said tirocinium ponere,[295] and if it were a success, he might devote himself more particularly henceforward to the art and practice of oratory.  No doubt all really ambitious young men, who aimed at high office and an eventual provincial government, would, like Caesar, endeavour to qualify themselves for the army as well as the Forum.  Cicero, however, whose instincts were not military, served only in one campaign, at the age of seventeen, and apparently he advised Caelius to do no more than this.  Caelius served under Q. Pompeius proconsul of Africa, to whom he was attached as contubernalis, choosing this province because his father had estates there.[296] It was only on his return with a good character from Pompeius that he proceeded to exhibit his skill as an orator by accusing some distinguished person—­in this case the Antonius who was afterwards consul with Cicero.[297]

To attain the skill in oratory which would enable the pupil to make a successful appearance in the Forum, he must have gone through an elaborate training in the art of rhetoric.  Cicero does not tell us whether he himself gave Caelius lessons in rhetoric, or whether he sent him to a professional teacher; he had himself written a treatise on a part of the subject—­the de Inventione of 80 B.C., the earliest of all his prose works—­and was therefore quite able to give the necessary instruction if he found time to do so.  It is not the object