his little moon are up to fifteen
miles high, causing a state of instability that is chronic. Walking down
those alabaster valleys was a more awesome experience than any galactic
vista I have ever encountered. Our aesthetic sense proved stronger than
common sense alertness and seven of us were buried in a rock slide.

* * * * *

Fortunately the great rocks formed a cavern above us. After two days we
were rescued. The others had suffered such minor injuries that they were
repaired before our craft landed on Nirva. I, though, unconscious and
feverish, was in serious condition from skin abrasions and a comminuted
cranium. Dr. Erics made the only possible prognosis. My skull had to be
removed and a completely new protoskin had to be supplied also.

* * * * *

When I came out of coma Marla was standing at my bedside, smiling down
at me. "Do you feel," she stumbled, "darling, I mean, do you feel the
way you did?"

I was puzzled. "Sure, I'm Treb Hawley, I'm your husband, and I remember
an awful fall of rocks but now I feel exactly the way I always have." I
did not even realize that further substitutions had been made and did
not believe them when they told me about it.

Now I _was_ an object of curiosity. Upon our return to Earth the
newsplastics hailed me as one of the most highly reintegrated
individuals anywhere. In all the teeming domain of man there were only
seven hundred who had gone through as many substitutions as I had.
Where, they philosophised in passing, would a man cease to be a man in
the sequence of substitutions?

Philosophy had never been an important preoccupation of mine. It was the
only discipline no further ahead in its really essential questions than
the Greeks of four thousand years ago. Oh certainly, there had been lots
of technical improvements that were fascinating but these were
peripheral points; the basic issues could not be experimentally tested
so they had to remain on the level of accepted or rejected axioms. I
wasn't about to devote much time to them when the whole fascinating
field of subatomic mirror numbers was just opening up; certainly not
because a few sensational journalists were toying with dead-end notions.
For that matter the newsplastics weren't either and quickly went back to
the regular mathematical reportage they do so well.

A few decades later, however, I wasn't so cocksure. The old Centaurian
virus had reap