I find this following passage to be quite illuminating to the study of slavery in Rome, and the relative loss of humanity and human body/mind that the slave endured. The slave was not a person, but rather a speaking tool.
“De fundi quattuor partibus, quae cum solo haerent, et alteris quattuor, quae extra fundum sunt et ad culturam pertinent, dixi. Nunc dicam, agri quibus rebus colantur. Quas res alii dividunt in duas partes, in homines et adminicula hominum, sine quibus rebus colere non possunt; alii in tres partes, instrumenti genus vocale et semivocale et mutum, vocale, in quo sunt servi, semivocale, in quo sunt boves, mutum, in quo sunt plaustra.”
– Varro, Dē Rē Rusticā 1.17
I have spoken about the four parts of a farm, which are connected with the soil, and about another four, which are outside of the farm and belong to agriculture. Now I will speak about those thing by means of which fields are cultivated. Some divide these things into two parts, into people and tools of people, tools without which people could not cultivate; others divide these things into three parts: a type of speaking tool, a half speaking tool, and a mute tool– the speaking tool, which are slaves; the half speaking, which are cow; and the mute tool, which are wagons.