I tried this back in the early '70's and got my nose rubbed in it. I may even have a letter from Ms. Norton on the subject. What she said, and what various analysts (Sandra Miesel?) have shown, is that (1) She uses common ideas/things rather than reinventing the universe for each book BUT BUT BUT ... they're STILL not the same universe. You can have Dipples and Zachatans, but they're just props. Same as Shakespeare used classical characters such as various gods and heros in some of his plays ... same name and character but no connection. (2) Unless it's a specific series like Solar Queen or otherwise a sequel to something ... THEN you can play "timeline."No argument here; that's why it is primarily for my own amusement.
And although I tremble at the thought of possibly contradicting the Author Herself outright, I have to maintain that you can play "timeline" with any author's works if they contain common elements.
To paraphrase something I read in Wilson and Shea's "Illuminatus Trilogy": Any set of seemingly connected works can be fitted into a consistent framework given sufficient ingenuity on the part of the person doing the fitting.
I don't lay claim to any great genius (I never did believe the IQ tests they gave me in grade school) but I am Irish, descended from a long, l-o-o-o-o-ng line of logic-twisters -- and earned my post-graduate degree during fifteen years as a civilian employee of the U.S. Navy. Believe me, the old saying (right way, wrong way... Navy way) is TRUE.
And with all due deference to the qualifications and expert knowledge of analysts such as Ms. Miesel (if she is the one who rapped your knuckles for your impertinence -- if not, my apologies to her in advance), I would simply say One Man's Mede Is Another Man's Persian. Common elements create a common omniverse, and the existence in the source material of parallel timelines creates the possibility that in the "Successor World Next Door" Andre Norton's cognate did intend to create a cohesive future history.
Respectfully -- but unrepentantly --
Michael B. Caffrey Stellae Nostrae Sunt!
