Slavery

Columella, On Farming, how to treat your slaves - utilitarian (slaves are your own investment) Slaves could buy freedom or be manumitted by owner on deathbed. Better to be slave than a free serf.

Slaves had own hierarchy, were able to be overseer. "Free men" became more popular than slaves over time. Slaves usually came from conquest, and as conquests declined, coloni arose. Theodosian Code systematized ways of treating coloni.