This page is part of my What is Science Fiction? site.

Hard versus soft ScF

"Hard" science fiction is a hotly-defended sub-genre whose definition is also in dispute, though there are probably fewer disputants than for the definition of ScF as a whole. Generally, it somehow means fiction in which the science is not merely necessary, but central: one half-joking definition says that you have to have had a scientific education in order to enjoy it. There are people who seem to use "hard" to denote any work that contains any science or technology, or is obviously not fantasy (or even, is not obviously fantasy); it may be that these people are suffering from "science envy" and believe that hard ScF is better than other ScF because it contains more science, so they try to boost their favourite ScF books by claiming that they are hard. Surely there is plenty of excellent soft ScF!

Brad Templeton says:

I would put it simply as "science and technology seem real and are 'characters' in the story". When I say characters, I mean that you notice and remember them as much as you would a memorable character. They're important to the story, it would not be the same without them.

Doug Tricarico goes into slightly more detail:

I'm partial to the idea that fantasy deals with the impossible, while SF deals with the possible; that hard SF deals with hardware while soft SF deals with wetware. (Hard: Hogan's Voyage From Yesteryear. Soft: Atwood's The Handmaid's Tale.) The best science fiction, however, deals with both aspects, applying the science to human behavior and systems. As Niven once said, "A good SF author invents the car; a great SF writer comes up with the traffic jam."

Another person (whose name I forget) applies the term "hard" to works where the author has gone to the trouble of showing us a way of life that has been shaped, or at least is different from ours, by the science or technology in the story. They instanced some of Bujold's books. I regard this as where the line should be drawn between all real ScF and "Mars Westerns" or "space fantasy", but have to admit that it's not very far from Brad's definition. Do you agree with me that there's a subtle but important difference?

Accuracy and Plausibility

Some vociferous readers hold that, to be truly hard, a work must stick to what was possible according to the scientific theories that were generally accepted as of the time it was written. My objection to this is that, as science advances, what we regard as possible will change, perhaps radically. Favourite examples: slightly over a century ago, it was believed impossible to convert mass into energy, and possible to determine the position of a particle to arbitrary accuracy without affecting its momentum. The least realistic books about the 21st or later centuries are those which assume that no more such changes in our knowledge will occur! (Well, perhaps that's the second least realistic category; the ones that really get my goat are the ones that assume that all the things we want to become possible (and only those things) will become so -- FTL travel, anti-gravity, etc. -- and nothing will become impossible.)

So I won't rule something out as hard ScF because we presently believe it to be impossible; rather, I see degrees of plausibility based on the extent to which accepted theories would have to be re-written. In particular, it seems to me legitimate to base a "hard" ScF story on an invented theory that explains some phenomenon which current theories (as of 1995) do not explain well, e.g. the solar neutrino deficit or the "missing" dark matter. One could use "Science-Based Science Fiction" for that which dreams up extensions of current theories (or dreams up whole new theories), and "Scientifically Accurate Science Fiction" for that which sticks rigidly to current theories.

Matt Austern comments:

I don't see that scientific accuracy has anything at all to do with genre distinctions. You see, one category I recognize is "science fiction that has inaccurate science". As I said, I'm a scientist, so of course I know more about science than most SF writers; picking technical holes in SF stories is an easy and largely pointless task. Almost all SF books I have read contain either errors or made-up science that contradicts things that are known today; most of the exceptions are books that are so vague that there isn't any substantive scientific content. At some point, if you know enough science and if you want to continue to enjoy SF, you just have to learn to stop caring. I don't see the value in defining SF so strictly that the set of "true" SF books becomes the empty set.
Matt has also said something to the effect that he doesn't see much point in distinguishing hard ScF from any other kind.


A weaker position allows extensions to presently accepted theories as long as it can plausibly be explained that they do not conflict with the evidence that supports these theories. This is, of course, more of a slippery slope than a definition.

Christian "naddy" Weisgerber offers this definition of "hard":

"SF that is written to a high degree of conformance with current scientific knowledge, where all extrapolation of new phenomena is plausible, self consistent, and limited in number and/or scope as to not reduce its effects to arbitrariness. The plot should center around the exploration of a scientific phenomenon, its applications, or generally the application of science and engineering to the solution of problems."

All the same, the "strict" definition of hardness is useful, and I have great respect for authors who can stick to it and produce interesting work. Really I'd like to see a change in terminology. There are, after all, works which avoid assuming any changes to current science simply because they avoid assuming much about science at all -- for example, some of the books about over-populated future Earths -- and I would hate to accord them the accolade of calling them "hard" while Niven's Neutron Star is denied it because he assumes FTL travel. (OK, for a "hard" writer, Niven proposes some remarkably implausible tech.) Some purists would probably apply the term "science fantasy" to works that go beyond currently believed science, and that leads us to discuss the distinction (if any) between ScF and fantasy.

It's an attitude

My own favourite definition is even looser than those above: it simply says that hard ScF is about how natural objects (and machines built out of them) behave in the author's invented world, while soft ScF is about how people (and societies built out of them) behave in an invented world. Note that the people may be human or non-human. The weakness here is that there are sciences whose subject matter is people, so if I accept anthropology as a science, I may have to accept, for example, The Dispossessed as hard ScF. Hmmm. You be the judge. Other people on rec.arts.sf.written have suggested that hard ScF is simply ScF written by and/or for people with the mindset of a "hard" (physical) scientist or engineer. I wish I could acknowledge the one who wrote
Hard SF is a form of alternate universe fiction, set in a world where the world-view of American engineers in the late twentieth century is a precise reflection of The Way Things Are.
I find the name Soren F. Petersen attached to it; hope that's right.
Since you've read this far, you may want to visit the forum I've created. I'd be especially interested to hear what you know about the history of the term "hard science fiction".
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