In I928, "The Skylark Of Space" by Edward E. Smith appeared in Amazing Stories, and was instantly recognized as an important milestone in science fiction.

Until then, stories involving space travel dealt almost exclusively with the solar system. Trips to the Moon and to Mars were the staples. Visitors from other stellar systems may have been mentioned (as in the case of the visitor from Sirius in Voltaire's " Micromegas") but these were trivial instances.

Smith, however, introduced interstellar travel as a commonplace thing and placed his heroes and villains within a space-frame that included the entire galaxy. It was the first time this had happened and the readers devoured it and demanded more. The "superscience story" became the hit of the decade. Smith held the lead in this respect for twenty years, although during the first half of his career, John w. Campbell was a close second.

Smith and Campbell viewed the galaxy as including many, many intelligent species. Almost every planet possessed them and Smith, in particular, was most inventive in dreaming up unearthly shapes and characteristics for his alien beings.

This "many-intelligence galaxy" is not as prominent in science fiction as it once was, but you may find it in contemporary television. In Star Trek and its lesser imitations, it sometimes seemed as though a spaceship could not travel in any direction at random, for a week, without coming across an intelligent species (usually inimical in one way or another.) The visual media are hampered in their ability to represent these aliens imaginatively, for somehow an actor usually exists under the makeup or plastic. The extraterrestrial creatures, therefore, if not human, were nevertheless clearly primate.

In this connection, though, the science fiction writer, Hal Clement raised an interesting question, which I think of as "Clement's Paradox."

The universe has existed for perhaps fifteen billion years, and if there are many civilizations that have risen here and there among its stars, these must have appeared at any time in the past twelve billion years (allowing three billion for the first to arise).

It should follow, therefore, that human explorers, when locating an extraterrestrial civilization, would be quite apt to find them anywhere from one to twelve billion years old in the vast majority of cases (assuming them to be very long-lived). If they were not very long-lived, but only endured, say, a million years or less before coming to a natural or a violent end, then almost all planets bearing such civilizations would show signs of the ruins of a long-dead one, or possibly a series of two or more sets of ruins.

To a lesser extent, in relatively young planetary systems, the civilization might not be ready to arise for anywhere from a million to a billion years.

The chance of encountering a civilization, then, that is at some level near our own would have to be very small.

And yet (and this is Clement's Paradox), science fiction writers consistently show alien civilizations to be fairly close in technological level to Earth's. They might be a little more primitive or a little more advanced, but considering the rate at which technology advances on Earth these days, it would seem that the aliens are not more than a few thousand years behind us at most, or a few hundred years ahead of us at best.

How enormous the odds are against that!

As far as I know, however, science fiction writers didn't worry about this. Certainly, I didn't. Since I began publishing in 1939, when Edward E. Smith was at the very height of his success (though John Campbell had just retired to the job of editing Astounding), I naturally tried my hand at the "many-intelligence" galaxy myself.

For instance, there was my eighth published story, "Homo Sol," which appeared in the September, 1940 Astounding. It dealt with a galactic empire consisting of the civilized beings from many, many planetary systems-each planetary system containing a different type of intelligent being. Each bore the name of the native star in the species name, so that there would be "Homo Arcturus," "Homo Canopus " and so on. The plot dealt with Earth's coming of technological age and the possible entry of Earthmen ("Homo Sol," you see) into the empire.

And now there came a struggle between John Campbell and myself. John could not help but feel that people of northwest European descent (like himself) were in the forefront of human civilization and that all other people lagged behind. Expanding this view to a galactic scale, he viewed Earthmen as the "northwest Europeans" of the galaxy. He did not like to see Earthmen lose out to aliens, or to have

Earthmen pictured as in any way inferior. Even if Earthmen were behind technologically, they should win anyway because they invariably were smarter, or braver, or had a superior sense of humor, or something.

I, however, was not of northwest European stock, and, as a matter of fact (this was 1940, remember, and the Nazis were in the process of wiping out the European Jews), I was no great admirer of them. I felt that Earthmen, if they symbolized these northwest Europeans according to the Campbellian outlook, might well prove inferior in many vital ways to other civilized races; that Earthmen might lose out to the aliens; that they might even deserve to lose out.

However, John Campbell won out. He was a charismatic and overwhelming person, and I was barely twenty years old, very much in awe of him, and very anxious to sell stories to him. So I gave in, adjusted the story to suit his prejudices and have been ashamed of that ever since.

Nevertheless, I didn't plan to have that happen again, ever. I wrote a sequel to "Homo Sol," which I called "The Imaginary," in which I evaded the issue by having Earthmen not appear (and Campbell rejected it). I wrote another story in which Earthmen fought villainous extraterrestrial overlords, and felt that would be all right, for the overlords were transparent symbols of the Nazis (and, as it happened, Campbell rejected that, too).

I continued to want to write "superscience stories" my way, however, and continued to probe for strategies that would allow me to do so without encountering Campbellian resistance.

I arrived at the answer when I first thought of my story "Foundation." For it, I needed a galactic empire, as in "Homo Sol," and I wanted a free hand to have it develop as I wished. The answer, when it came to me, was so simple, I can only wonder why it took me so long to reach it. Instead of having an empire with no human beings as in "The Imaginary," I would have an empire with nothing but human beings. I would not even have robots in it. Thus was born the "all-human galaxy."

It worked remarkably well for me. Campbell never raised any objections; never suggested that I ought to insert a few alien races; never asked why they were missing. He threw himself into the spirit of the stories and accepted my galactic empire on my terms, and I never had to take up the problem of racial superiority/inferiority.

Nor did I spend time worrying about the rationale behind the all-human galaxy myself. I had what

I wanted, and I was satisfied.

I did not ask myself, for instance, why it was that human beings were the only intelligent species in the galaxy. As it happens, it is possible that though planets are extremely numerous, relatively few are habitable; or that though many planets may be habitable, few may develop life; or that though many planets may be lifebearing, few indeed may develop intelligent life or civilizations. Nevertheless, I made no effort whatsoever to state any of this explicitly as explanation for what I was describing. It is only with my new novel Foundation's Edge, written forty years after the series had begun, that I have started to explore the rationale behind it.

Nor did I ask myself, at the start, if the idea were a novel one. Years later, I began to think that no one before myself had ever postulated an all-human galaxy. It seems to have been my invention (though I stand ready to be corrected in this by some SF-historian more knowledgeable than myself).

If I did indeed invent the concept, it is a useful one, quite apart from the role it played in the duel between Campbell and myself (a duel which Campbell never knew existed). By removing the alien element, the play and interplay of human beings can be followed on an enormous canvas. Writers can deal with human interactions (only) on different worlds and within different societies and it gives rise to interesting opportunities of all sorts.

And, what is more, the all-human galaxy offers a way of getting around Clement's Paradox- perhaps the only way of doing so.