Final answer:
In legal terms, if Mary's property was 'in rem,' it signifies that legal proceedings or claims are made against the property itself, not an individual, determining rights over that property.
Step-by-step explanation:
If Mary's property was described as being "in rem," this means that legal action or jurisdiction is directed toward the property itself, rather than a specific individual. This concept often relates to matters where the rights to a piece of property are the primary concern, such as in the context of property taxes or disputes over ownership. In legal contexts, an in rem action ensures that any judgments made affect the property and its ownership status, which can involve inhabitants' property such as houses, gardens, mills, fields, vineyards, etc. as mentioned in the reference material. The provided passages illustrate historical examples where property and its ownership played crucial roles in legal and societal norms, from detailed declarations for tax purposes to provisions in wills as per historical codices. Moreover, it suggests the varying perceptions of property and ownership throughout history, whether that property was real estate or, regrettably, human beings, as in the sale of individuals during slave auctions.