“There is none, not if you agree that like causes produce like effects. All planets are produced by the same basic process, and so every Sol-type star must have a system like this one. And every Earth-type planet must produce the same general forms of life—because two processes beginning with the same initial conditions must run the same course.”

“But how can the initial conditions be so much alike?”

“They are, in at least half the cases. There are deviations of greater or less degree, but over half the GO-type stars explored so far have been found to have planets similar to Taitha inhabited by an intelligent race similar to our own—and Earth is such a one.” Gor Haml’s eyes rested speculatively on the President: “We were astonished at this ourselves, when we first began exploring, but the fact was there. Now we know the reasons and see that such similarity is inevitable in this universe, but I cannot explain the philosophy to you. A thousand years from now, Earthlings should be able to understand it—but not at your present stage of development.”

“I begin to see how you were able to learn about us so quickly,” said Brackney. “You knew just about what to expect and what to look for.”

“That is part of it, to be sure. Also, we have the benefits of a psychological science evolved to a point that might seem miraculous to you. It includes all human knowledge, which is after all only a function of the human organism, and integrates it according to principles your scientists and philosophers have not yet imagined. You have the germ of it in your experimental and analytical psychology, in semantics and symbolic logic, in physical and biological sciences, yes, and in some of your philosophical speculations. But you have not begun to exploit the potentialities of your own nervous systems. Taithans have no more inherent intelligence than Earthlings, but they know how to use it; just as a caveman was inherently capable of using, say, tensor analysis, but the knowledge did not exist for him. Thus we can perform such apparent feats of legerdemain as understanding and classifying a planet in a month’s hard work.”

“I see,” nodded Brackney. “I can even guess your main line of approach—simply reading tons of written material of every kind, at some fantastic speed, and analyzing the information, both direct and indirect, it contains.”

“That is one important line, at least,” smiled the Taithan. “I might add that history books are the leading source of the knowledge we are after.”

There was a moment of silence. The Earthlings sat looking at the strangers, seeking some sign of foreignness or of godlike power or anything, rather than the score of weary-looking, ordinary men before them. Brackney, with a politician’s sensitivity to moods, could not, escape the nagging conviction that the Taithans were depressed. They look at us as if they felt sorry for us!

He said, more to break that awkward stillness than for any other reason: “I suppose this is a rather meaningless question, but how far ahead of our civilization is yours? I mean…well, of course we’re contemporaries, but what time equivalent separates us—?” He stopped, acutely aware of his own lack of terminology.