Wright points out that neither Clarke nor Bradbury were Campbell authors. "...Arthur C. Clarke is from an older tradition of science fiction than Heinlein and Asimov, and is an heir to H.G. Wells..." Bradbury, meanwhile, "...was a man before his time, and fathered a younger tradition. He was 'New Wave'...years before the New Wave was new."
In contrast to the sci-fi stories that preceded his influence on the genre, which "were mostly boy’s adventure stories set in space...Campbell established a new type of story, less about weirdness and wonder and more about what we now call 'Hard' Science Fiction..."
Hard science fiction, says Wright, "consists of two elements...first, a social or philosophical commentary about man’s place in the universe...second, a fascination with the nuts and bolts of legitimate speculation into the near future of technical advance..." Campbell was the first to popularize stories combining both elements.
Describing the definitive mood and spirit of Campbellian tales is difficult these days, Wright contends, because they were "an extension of the scientific optimism and classical liberalism of the time." A further characteristic of Campbell's stories was "...a touching childlike faith in Theory, and, for conservatives (in the brilliant words of William Briggs) 'Love of Theory is the Root of All Evil.'"
Wright goes on to take issue with the prevailing definition of hard SF, observing that this classification is based on only one story element: world building.
...[T]he common consensus is that 'Hard SF' is any story whose core revolves around some real science...and that 'Soft SF' is any story whose core revolves around the humanities or some less rigorous discipline...[T]his is insufficient, since...the grouping of certain tales and novels into sub-genres should also tell you something of the other elements of the story, including the plot, character, and theme.Besides world building, Wright asserts that Campbellian SF can be recognized by similarities in plot, characterization, and theme. He cites van Vogt's "The Black Destroyer" as the first of these stories. "The tale contained in embryo the elements of the typical Van Vogt tale: superhuman powers...the interest in psychology and parapsychology, the scope of action, and the breathless pacing..." Slan and World of Null-A also stand as conspicuous landmarks of Campbellian SF.
"...[M]ost of these stories," Wright points out, "are not very 'Hard' at all...replete with unscientific gobbledygook as mindreading guns, time travel, teleportation, and the transfer of human memory from clone to clone."
Wright identifies three philosophical underpinnings of all Campbell stories: malleable human nature that is open to advancement through technology, lead characters who solve problems through intelligence guided by a properly calibrated moral compass, and finally, the optimistic theme "which said that men were moral creatures who...could become large enough in their time to conquer the stars."
"For Van Vogt, the larger brain of the Martians of H.G. Wells, or the cold remorselessness of the superman imagined by Nietzsche were of no account if not also wedded to a greater moral sense."
"This," says Wright, "was not Arthur C. Clarke’s view...that man would eventually evolve into something glorious in its own way but ultimately inhuman, and certainly not Ray Bradbury’s view, which was...more interested in the joys of home and hearth and the mysteries of the woods beyond the backyard..."
It isn't due to any nuts-and-bolts realism of that van Vogt merits his title as the third of Campbell's Big Three. "...'Hard SF' is not just any story that puts technology at its heart," concludes Wright. "The heart of Hard SF is this cynical optimism, the paradox of men whose feet are firmly planted on the ground, and yet whose hands reach for the stars."