Four Themes And Six Authors

I need hardly repeat that my favourite two kinds of sf are time travel, provided that it is presented consistently, and future histories. I suppose that the third major sf theme is space travel with alien invasions of Earth as a specific sub-theme. HG Wells, Olaf Stapledon and Poul Anderson all describe Martian invasions of Earth although Anderson also presents extra-solar economic invasion in "Soldier From The Stars," where militarily superior humanoid aliens do not conquer Earth but sell their services to the highest bidder among Terrestrial governments and are paid in Terrestrial currencies...

The four themes of space travel, time travel, alien invasion and future history provide a template for comparing three British authors and three Campbell future historians. Thus, Wells wrote:

The First Men in The Moon

The Time Machine (travel through the whole future of life on Earth)

The War Of The Worlds

The Shape of Things to Come (a future historical turning point)

Stapledon incorporated space travel, time travel and Martian invasion into Last And First Men, a history of the entire future of mankind, then wrote a cosmic history, Star Maker.

CS Lewis wrote:

Out Of The Silent Planet (travel to Mars)

"The Dark Tower" (inadequate discussion of time travel)

Perelandra (Terrestrial evil invading sinless Venus)

That Hideous Strength (reply to Wells' and Stapledon's future histories)

Robert Heinlein wrote:

three "first men in the Moon" stories

three circular causality paradox stories

The Puppet Masters

the Future History

James Blish wrote:

Welcome To Mars

"The City That Was The World"

VOR

Cities In Flight, The Seedling Stars and the Haertel Scholium

Poul Anderson wrote:

Well, we all know what Poul Anderson wrote