TOPIC: Scope management plan as an input for define scope

I am watching video tutorial 05.03 Define Scope. One of the inputs for the Define Scope Process is the Scope Management plan(as a part of the Project Management Plan). One of the components of the process for formulating the scope management plan seems to be a defined scope (Cycle of "Define Scope-Develop-Monitor and Control-Validate"). This seems illogical. Like a violation of the chicken and the egg concept

John,

Where exactly does it say that "One of the components of the process for formulating the scope management plan seems to be a defined scope"?