In recent writing on the city states, American scholar Rodney Stark emphasizes that they married responsive government, Christianity and the birth of capitalism. He argues that these states were mostly republics, unlike the great European monarchies of France and Spain, where absolute power was vested in rulers who could and did stifle commerce. Keeping both direct Church control and imperial power at arm's length, the independent city republics prospered through commerce based on early capitalist principles, ultimately creating the conditions for the artistic and intellectual changes produced by the Renaissance.