What do we know of Cato, the Younger, man of principle, and tradition, a Senator who defended the Roman republic against Caesar?

Some may know him through Addison's play, "Cato, a Tragedy" which was popular during the Founding, widely quoted--"Give me liberty or give me death!"--and Washington had it performed at Valley Forge.

Go here for a talk by the authors of the new book Rome's Last Citizen: The Life and Legacy of Cato, Mortal Enemy of Caesar.