What assumptions were being made by Frankfurter with regard to the U.S. version

What assumptions were being made by Frankfurter with regard to the U.S. version of democracy?
Were these assumptions based, in turn, on other assumptions?
Have Frankfurter’s assumptions been the assumptions guiding court decisions?
Were Frankfurter’s assumptions the same as the assumptions of most U.S. citizens about the “branches” of government and the relationships among them?
Do you believe there should be a strict separation of powers between the judicial. executive and legislative branch? Why?
The book is Criminal Justice Masterworks by Panzarella and Vona