ing and go _up_ the
hyper-tube. You will have all his memories, his hopes, his fears, his
_sense of identity_. Unless you know--beyond any trace of doubt--who
_you_ are, the result is insanity."

* * * * *

The Senator puffed his pipe for a moment, then shook his head. "It
sounds like Oriental mysticism to me. If you can travel in time, you'd
be able to change the past."

"Not at all," Camberton said; "that's like saying that if you read a
book, the author's words will change.

"Time isn't like that. Look, suppose you had a long trough filled with
supercooled water. At one end, you drop in a piece of ice. Immediately
the water begins to freeze; the crystallization front moves toward the
other end of the trough. Behind that front, there is ice--frozen,
immovable, unchangeable. Ahead of it there is water--fluid, mobile,
changeable.

"The instant we call 'the present' is like that crystallization front.
The past is unchangeable; the future is flexible. But they both exist."

"I see--at least, I think I do. And you can do all this?"

"Not yet," said Camberton; "not completely. My mind isn't as strong as
Wendell's, nor as capable. I'm not the--shall we say--the superman he
is; perhaps I never will be. But I'm learning--I'm learning. After all,
it took Paul twenty years to do the trick under the most favorable
circumstances imaginable."

"I see." The Senator smoked his pipe in silence for a long time.
Camberton lit a cigaret and said nothing. After a time, the Senator took
the briar from his mouth and began to tap the bowl gently on the heel of
his palm. "Mr. Camberton, why do you tell me all this? I still have
influence with the Senate; the present President is a protege of mine.
It wouldn't be too difficult to get you men--ah--put away again. I have
no desire to see our society ruined, our world destroyed. Why do you
tell me?"

* * * * *

Camberton smiled apologetically. "I'm afraid you might find it a little
difficult to put us away again, sir; but that's not the point. You see,
we need you. We have no desire to destroy our present culture until we
have designed a better one to replace it.

"You are one of the greatest living statesmen, Senator; you have a
wealth of knowledge and ability that can never be replaced; knowledge
and ability that will help us to design a culture and a civilization
that will be as far above this one as this one is above