About 93 CE, the Roman emperor Domitian (Titus Flavius Domitianus) declared that he would penalize slave owners who used their slaves in the lucrative business of teaching grammar and rhetoric. Winter (1997) provides an insightful discussion of the sophists’ teaching industry of that time. Perhaps celebrity teachers were leveraging their market position by using slaves under them to provide teaching. That would be similar to the use of graduate students in prestigious research universities today.