1950J. D. MacDonaldShadow on Sand in Thrilling Wonder Stories Oct. 27/1
We have made the basic and very important discovery of a twin planetary system corresponding to our own, separated from us only by a symbolic logician’s definition of reality. This is not a completely physical and technical phenomenon. It is a philosophical phenomenon. In simplest terms the formula can be expressed this way: The twin world exists because any definitive explanation of reality presupposes alternate realities. Thus the doorway was achieved by the creation of unreality. Call it negative matter if you will. A sphere where there is no reality must, through the application of the basic formula, be a bridge between realities.
1951J. D. MacDonaldCommon Denominator in Galaxy Science Fiction July 22/1
The Argonauts, as they came to be called, were pleasantly similar to mankind. It was additional proof that only in the rarest instance was the life-apex on any planet in the home Galaxy an abrupt divergence from the ‘human’ form.
1950J. D. MacDonaldShadow on Sand in Thrilling Wonder Stories Oct. 26/2
And just in case we fail I suggest that we contact the A-list of all League personnel and advise them to ready themselves for basic flight procedure. We have statistically determined that even with maximum efficiency, one in ten on the A-list will be spaceborn [sic] in time but I feel that this is a necessary move.