What is not yours is not yours?

"Not Yours Is Not Yours" isn't a single, easily-defined thing. It's ambiguous and could refer to several interpretations:

• A philosophical concept: This phrase broadly encapsulates the idea of respecting property rights and not taking what doesn't belong to you. It's a basic tenet of many ethical and legal systems. It speaks to honesty, integrity, and the importance of individual ownership.

• A potential title: The phrase could be the title of a book, a film, an art exhibition, a song, or any other creative work exploring themes of ownership, theft, borrowing, sharing, and the ethical dilemmas surrounding these actions. Without more context, it's impossible to know which (if any) specific work this refers to.

• A proverb or saying: While not a widely known proverb, the phrase functions similarly to others emphasizing honesty and respect for others' possessions. It could be used informally to express this sentiment.

To provide more specific information, you would need to provide more context. For instance, are you thinking of a particular book, movie, or artwork with that title or a similar phrase? Knowing the context will allow for a much more accurate and helpful response.