If for some strange reason you take an interest in the legal aspects of Roman manumission you can easily find out that in the Republic, there were three methods which Roman masters could use to free their slaves. These methods are manumissio vindicta, manumissio censu and manumissio testamento. A number of Roman jurists assert that the Twelve Tables, an early collection of Roman laws, contained laws about how to handle manumission by testament, that is, when masters wanted to free their slaves in their wills. Since the Twelve Tables were likely written in the middle of the 5th century, they are commonly given the date of 451/0 BCE, such a law would appear to be a good candidate for the earliest form of manumission.
However two Roman legal scholars, Buckland and Watson, provide some very intriguing arguments for why we should think that the two other forms of manumission are earlier. What are these other forms of manumission? Manumissio vindicta is basically a sham trial: the slave-owner finds a witness who is willing to assert that the slave in question was wrongfully enslaved and therefore deserves to go free and be listed as a Roman citizen. The slave-owner and the witness go before a magistrate, who listens to their case. However, when it comes time for the slave-owner to present his case, he is instead silent; basically, he throws the case. Manumission by census also involves deception. When the censor comes by to collect names for the census, the master testifies that his slave is a Roman citizen and then the censor enters the slave’s name in the census. According to both Buckland and Watson, the deception of the state that is at the core of both these processes alludes to a time when the Romans did not grant citizenship to manumitted slaves. To get around this problem, Roman slave-owners used these furtive techniques. It is quite easy to imagine why they would want to do so: they could easily want to enfranchise certain slaves because it was quite possible for a slave-owner to father a son with a slave woman and then want to recognize that son as his heir.
How does manumission by testament work into this? Well, after enough time and enough slave-owners enfranchise their slaves through these furtive techniques, it becomes acceptable for former slaves to become citizens. However, this is not to say that it immediately became acceptable for a master to simply declare that his slave was now free and a citizen, as such a process would not have any sort of legal record. Hence manumission by testament. Since a will was a document that a family had already committed to preserving, the Romans could refer to these wills if they wanted to check if a slave had actually been freed by a master. There was apparently some pushback by Romans about this practice, as the Twelve Tables were necessary to confirm that wills had the authority to assure the freedom of slaves.
However two Roman legal scholars, Buckland and Watson, provide some very intriguing arguments for why we should think that the two other forms of manumission are earlier. What are these other forms of manumission? Manumissio vindicta is basically a sham trial: the slave-owner finds a witness who is willing to assert that the slave in question was wrongfully enslaved and therefore deserves to go free and be listed as a Roman citizen. The slave-owner and the witness go before a magistrate, who listens to their case. However, when it comes time for the slave-owner to present his case, he is instead silent; basically, he throws the case. Manumission by census also involves deception. When the censor comes by to collect names for the census, the master testifies that his slave is a Roman citizen and then the censor enters the slave’s name in the census. According to both Buckland and Watson, the deception of the state that is at the core of both these processes alludes to a time when the Romans did not grant citizenship to manumitted slaves. To get around this problem, Roman slave-owners used these furtive techniques. It is quite easy to imagine why they would want to do so: they could easily want to enfranchise certain slaves because it was quite possible for a slave-owner to father a son with a slave woman and then want to recognize that son as his heir.
How does manumission by testament work into this? Well, after enough time and enough slave-owners enfranchise their slaves through these furtive techniques, it becomes acceptable for former slaves to become citizens. However, this is not to say that it immediately became acceptable for a master to simply declare that his slave was now free and a citizen, as such a process would not have any sort of legal record. Hence manumission by testament. Since a will was a document that a family had already committed to preserving, the Romans could refer to these wills if they wanted to check if a slave had actually been freed by a master. There was apparently some pushback by Romans about this practice, as the Twelve Tables were necessary to confirm that wills had the authority to assure the freedom of slaves.