Final answer:
Federalists promised a Bill of Rights and highlighted the government structure with checks and balances in the Constitution to protect individual liberties and ease Anti-Federalists' fears.
Step-by-step explanation:
The Federalists eased Anti-Federalist fears by promising to add a Bill of Rights to the Constitution, protecting individual liberties. This promise ensured that specific rights would not be infringed upon by the new federal government. Moreover, the structure of the government itself, with its division of powers, was designed to prevent tyranny with built-in checks and balances. Federalist Papers like No. 51 argued that the new government could not grow too powerful due to these internal safeguards, aiming to further assure the public and Anti-Federalists of the safety of individual freedoms under the Constitution.