A proposal to replace Article II of the UU Bylaws (which in turn will replace the Seven Principles and Six Sources) will be voted on by UU delegates to UU General Assembly in June. The agenda for Article II is outlined here.

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EDIT:

The proposal of the Article II Study Commission is a significant rewrite of Article II in the UU Bylaws. It fact, it does replace both the Seven Principles and the Six Sources.

More information can be found on the Study Commission website. They are currently accepting feedback through an online form, until April 30.

The website with essays is: https://savethe7principles.wordpress.com/. (And to correct an assumption some people made, I had nothing to do with the creation of the website.)