Which friendly rival did Cicero argue against?

Cicero's primary friendly rival in oratory and legal debate was Hortensius. The two men were prominent figures in the early Roman Republic's legal and rhetorical landscape. Hortensius was known for his skill in rhetoric, and he often opposed Cicero in court cases, setting up a competition that was marked by mutual respect and admiration despite their rivalry.

Cicero considered Hortensius a benchmark against whom he measured his own oratorical abilities. Their relationship illustrates how competition can coexist with friendship, particularly when both individuals are striving for excellence in the same field. Cicero's discussions and writings about their exchanges often highlight the respect he held for Hortensius as both a politician and orator, making this rivalry significant in Cicero's development as a public figure and his thoughts on eloquence.

The other figures listed, like Brutus, Catulus, and Casca, had different relationships with Cicero. Brutus was an ally but became a political adversary during the late Republic. Catulus was more of a contemporary colleague, and Casca was known primarily for his involvement in the assassination of Julius Caesar, which did not involve the same kind of oratorical rivalry that characterized Cicero's relationship with Hortensius.