Final answer:
Justice Brown most likely defined the term slavery in his argument to argue that the Thirteenth Amendment was not being violated by segregation practices, thereby upholding the 'separate but equal' doctrine.
Step-by-step explanation:
The most likely reason why Justice Brown defines the term slavery in his argument is: B. Justice Brown defines the term slavery because making a technical term of slavery allows him to argue that the Thirteenth Amendment is not being violated.
By establishing a specific definition of slavery, Justice Brown can draw a distinction between the institution of slavery, which the Thirteenth Amendment abolishes, and the policies of segregation, which he could then argue do not constitute a form of slavery. '
This legal differentiation was key in justifying the 'separate but equal' doctrine and upholding segregation in the Plessy v. Ferguson case. It is crucial to recognize that this definition enabled the Supreme Court to protect segregation practices without explicitly endorsing the reintroduction of slavery, as prohibited by the Thirteenth Amendment. Therefore, such legal interpretations had profound impacts on civil rights and race relations in the United States well into the 20th century.