There were sixteen letters of Brutus written by Robert Yates. He used Brutus as a pseudonym because of the historical association of that name. Brutus was the Roman who had led the plot against Julius Caesar. Brutus and the plotters had killed Caesar because they felt he was destroying the Roman Republic and creating a monarchy dangerous to the rights of the Romans. Yates and other antifederalists felt that the Constitution was dangerous to the rights of Americans.
Yates believed that strong central governments were dangerous to the rights of the people. He felt that the British government had been strongly centralized and had therefore not really been attentive to the needs of the people in far-flung areas like the American colonies. He feared that the strong central government set up by the Constitution would do the same. It was for this reason that Yates demanded a bill of rights. He argued that it was necessary for the Constitution, at the very least, to have a listing of rights that the federal government could not infringe upon.
The “Letters of Brutus” then, said two main things. First, they said the new Constitution was dangerous. Second, they said that if it could not be defeated, it at least needed a bill of rights to protect the people from abuses by the government.