Final answer:
The belief in keeping religious faith private and separate from public policy is associated with Logical Positivism and the American constitutional principle of separating Church and State.
Step-by-step explanation:
The belief that religious faith must remain a private affair, especially when discussing public policy, can be attributed to a school of thought within philosophy that separates personal beliefs from empirical and logical reasoning, as exemplified by Logical Positivism. The Logical Positivists, such as the Vienna Circle, argued that religious language was meaningless because it could not be verified through experience or observation.
This separation of the private sphere of religion from the public sphere of governance was also supported by the US Constitution's First Amendment, which was designed to prevent government entanglement with religion, establishing a "wall of separation" between Church and State. This notion has evolved over time to rigorously safeguard against the government's role in religious matters, ensuring that religious freedom does not infringe on the rights and well-being of others.