ove." The founders of our modern religions were not fools;
they simply did not have the tools at hand to formulate their
knowledge properly. As understanding increases, a critical point is
reached, which causes a qualitative change in the human mind.

First, self-understanding must come. The human mind operates through
similarities, and the thing most similar to any human mind is itself.
The next most similar thing is another human mind.

From that point on, all objects, processes, and patterns in the
universe can be graded according to their similarity to each other,
and, ultimately, to their similarity to the human mind.

Two given entities may seem utterly dissimilar, but they can always be
linked by a _tertium quid_--a "third thing" which is similar to both.
This third thing, be it a material object or a product of the human
imagination, is called a symbol. Symbols are the bridges by which the
human mind can reach and manipulate the universe in which it exists.
With the proper symbols and the understanding to use them, the human
mind is limited only by its own inherent structural restrictions.

One of the most active research projects of the S.M.M.R. was the
construction of a more powerful symbology. Psionics had made
tremendous strides in the previous four decades, but it was still in
the alchemy stage. So far, symbols for various processes could only be
worked out by cut-and-try, rule-of-thumb methods, using symbols
already established, including languages and mathematics. None were
completely satisfactory, but they worked fairly well within their
narrow limits.

As far as communication was concerned, the hashed-together symbology
used by the S.M.M.R. was better than any conceivable code. The
understanding required to "break" the "code" was well beyond the
critical point. Anyone who could break it was, _ipso facto_, a member
of the S.M.M.R.

Most people didn't even realize that a conversation was taking place
between two members, especially if a "cover conversation" was used at
the same time.

* * * * *

MacHeath's verbal discussion of the testing of the nuclei accelerator
was just such a cover. Even before he had cracked the air lock, he had
known that Dr. Theodore Nordred was standing on the other side of the
thick wall.

MacHeath pushed the heavy door open on its smooth hinges. "Oh, hello,
Dr. Nordred. How's everything?"

The heavy-set mathematician smiled pleasantly