Premise for all else that he is going to argue

He describes the premise for all else that he is going to argue in this following sentence:
Redacted and introduced by John Beardsley, Editor in Chief, the Winthrop Society Quarterly. Copyright 1997. The Introduction and Gov Winthrop's writing appear here with the kind permission of Mr. Beardsley. You are invited to visit the web site of the The Winthrop Society.