Science fiction is commonly defined as a literary or cinematic genre in which fantasy, typically based on speculative scientific discoveries or developments, environmental changes, space travel, or life on other planets, forms part of the plot or background. However, to keep things simple, fans often use certain terms to distinguish between important subtypes. Here we take a look at the terms 'hard sf' and 'soft sf'.

It should be stressed that as in any creative enterprise, there is not really a 'line' dividing subtypes. Rather, there is a continuum, with 'hard sf' at one end shading through to 'soft sf' at the other. One often-used feature is the overt presence of technology. This specifically distinguishes Science Fiction and Fantasy from the works of authors such as JRR Tolkien with his hobbits roaming Middle Earth or Terry Pratchett's Discworld, where it is the overt presence of magic which defines the genre¹. Certain stories cross even that boundary - Anne McCaffrey's Pern novels are an example, in that they feature technology and magic in the same setting. This goes to show that the lines, such as they are, can be quite fuzzy.

sf v Sci-fi

Science fiction fans read 'sf'² or 'sci-fi'. Sci-fi (pronounced 'sigh-fie' by most, and 'skiffy' by hardcore fans³) is a term with a couple of specific meanings. For most people it is interchangeable with 'sf' or 'science fiction'. For a certain breed of fan it is a very specific, technical term of derision used to denote that which they regard as not 'proper' sf. Reasons depend on the fan, but can include poor writing, excess of technical detail at the expense of story, or transparent attempts to use sf trappings to get mass-market appeal.

Hard sf

Hard sf, in general, attempts to stick as close as possible to real-world scientific principles. Few basic assumptions are made that are outside the realms of believable (at least in theory) science. This requires a limited suspension of disbelief on the part of the reader. Once this principle is established, the author then deals with the consequences of these assumptions. Examples of common assumptions include:

• Aliens exist and have signalled (although not visited) Earth
• Bussard Ramjets work
• Some form of 'faster than light' drive is possible
• Time travel is possible

Hard sf eschews the deus ex machina (God from the machine) endings possible in softer sf or science fantasy ('Use the Force, Luke' from Star Wars), preferring characters to use their ingenuity to get out of jeopardy.

Hard sf is also generally 'directly' concerned with the consequences of a particular aspect of technology, rather than simply using it as a backdrop to a story which could have been told in any setting. For instance, the movie Twelve Monkeys is hard sf, as there is simply no way this story could have been told without time travel technology.

Because of the thorough knowledge of science required to do hard sf convincingly, it is often the case that authors are in fact highly qualified working scientists. Examples include Isaac Asimov, Stanislaw Lem, Gregory Benford, Robert L Forward and Carl Sagan. On the other hand, plenty of good hard sf has been created by writers who have made a career from writing. They include Larry Niven, William Gibson⁴, Bruce Sterling and Harlan Ellison.

True hard sf in film is rare. Examples include 2001:A Space Odyssey, Blade Runner, Terminator, Twelve Monkeys, Contact and (arguably) Jurassic Park. In television, hard sf is equally rare. Babylon 5 is much closer to hard sf than its main competition, Star Trek. Certain Dr Who stories (Genesis of the Daleks) and, perhaps oddly, Red Dwarf, could be considered hard sf.

Soft sf

This genre takes the rules less seriously. It is still recognisably sf, in that it can feature spacecraft, computers, robots, tales of the future or past and extrapolations from current technology. The concern for scientific accuracy is much less important and, in general, is allowed to be ignored if it gets in the way of the story. It therefore requires a greater suspension of disbelief on the reader's behalf. This is not to say it is in any way inferior to hard sf. Ultimately, what matters is the story, and the quality of the writing.

It is very debatable what counts as soft sf writing, as there is a very fuzzy boundary between hard and soft. Typical assumptions made in soft sf include:

• Aliens exist and have visited Earth

• Teleportation along the lines used in the television series Star Trek is possible

• Some form of coherent society spanning the Galaxy exists

• Human/alien hybrids are possible

Soft sf is less concerned with technology. With an over-riding emphasis on the story, the technology is simply a backdrop against which the story is played out, and it is possible to transplant the story to a different genre without difficulty. For example, HG Wells' classic tale The War of the Worlds is soft sf - it assumes Martian life - but the story is basically one of invasion by a technologically superior force.

This lesser adherence to 'rules' in soft sf leads to great freedom in storytelling. However, it also leads to the danger of the deus ex machina - setting up your characters in jeopardy, then doing the equivalent of saying 'and with one bound, they were free'. This often puts non-fans off the genre altogether, and is often a symptom of lazy or hasty plotting. On the rare occasions it is done well, it can be very effective. Douglas Adams, writer of The Hitchhiker's Guide to the Galaxy⁵, noted in an interview how difficult it was to write the convincing transition from prehistoric Earth to the Test Match at the beginning of Life, the Universe and Everything so that the reader was not put off by the seeming simplicity of the escape.

Soft sf in film is quite common. Examples include Star Wars, Buck Rogers, Flash Gordon, Independence Day, all incarnations of Star Trek, most of Dr Who, and many more.

Genres within Genres

Although most sf stories can be placed somewhere along the scale from hard to soft, there are dozens of sub-types within those two categories. These include such things as:

• Space opera⁶
• Post-apocalypse
• Lost or isolated societies
• Groups which have reverted to a lower level of technology
• Cyberpunk
• Steampunk
• Alternate History
• Golden Age
• New Wave
• Utopian
• Dystopian

This list is incomplete, and many stories overlap several of these genres. Also, by its nature sf is evolving constantly, with the occasional massive leap. Arguably the last such paradigm shift was with the cyberpunk movement of the 1980s.