Modern republicanism - distinguished from its classical counterpart by its commercial character and jealous distrust of those in power, by its use of representative institutions, and by its employment of a separation of powers and a system of checks and balances - owes an immense debt to the republican experiment conducted in England between 1649, when Charles I was executed, and 1660, when Charles II was crowned. Though abortive, this experiment left a legacy in the political science articulated both by its champions, John Milton, Marchamont Nehdham, and James Harrington, and by its sometime...