Special Circumstances, abbreviated SC, is a "secret service"-type organisation that exists within the fictional anarchist utopian science fiction civilisation known as the Culture. It forms a background and plot device in several novels and shorter works of Iain M. Banks.
Special Circumstances is part of a larger fictional Culture organisation called Contact, which coordinates Culture interactions with (and in) other civilisations. SC exists to fulfil this role when circumstances exceed the moral capacity of Contact, or where the situation is highly complex and requires highly specialized skills, such as in The Player of Games. Special Circumstances also does the "dirty work" of the Culture, a function made especially complicated by the normally very high ethical standards the Culture sets itself. SC acts in a way that has been compared with the democratising intentions of real-world liberal intent on overcoming the world's (and especially other nation's) evils by benign interference.
In the novels, Special Circumstances often provides the main plot device linking the Culture and other civilisations being intervened in. The "good works" (for which Special Circumstances does the dirty work) are the wider plot device for allowing interaction between the advanced Culture and the "barbaric" societies it tries to improve. In the same vein, Banks has noted that the perfect society of the Culture creates well-adjusted, content people—who are (for story purposes) rather boring. Therefore, many of the Culture novels deal with outside agents or mercenaries in the employ of Special Circumstances.
Interventions by SC usually take the form of covert operations (military or otherwise) designed to strengthen or weaken factions within less advanced civilizations. Special Circumstances does not always "play nice" like the rest of the Culture. Their activities have been known to include assassinations, manipulation, and blackmail.
Typically, the interventions aim to improve the situation of less advanced civilizations, and to get them closer to the Culture ideal. Sometimes interventions may also be intended to nip future challenges to the Culture in the bud (The Player of Games). While the Culture believes that it can statistically prove that most interventions achieve this end, operations are not always successful. Some, as in Look to Windward, may even be disastrous for the intervened civilization.