Dark satire is a form of satire that includes themes and ideas that are considered dark or morbid, and which often uses these ideas to explore complicated or morally ambiguous issues. In basic structure or purpose, this is much like any other form of satire, in which humor is used for ironic purposes to make a statement about a certain idea or practice. Dark satire, however, uses dark humor that is not necessarily meant to be funny, but to use humor as a way to offset horror or unpleasantness. The essay A Modest Proposal by Jonathan Swift can be seen as this type of satire, as it proposes cannibalism as a solution to food shortages for the poor.
Much like other forms of satire, dark satire is the use of humor, though in this case dark humor, to assist in the delivery of a particular message or criticism. For example, someone might use satire to point out flaws in a particular political system, such as a joke that satirizes an ineffectual political process by equating it to people trying to keep a boat from sinking by drilling holes into the boat. In dark satire, however, the images and ideas presented to make a point are often darker and grimmer in tone.
This is similar to dark humor in some ways, in which a joke is made that is not meant to be inherently funny but to make light of something horrific. In dark satire, a ruthless political leader might be satirized through the use of much darker and unpleasant metaphors. The Bret Easton Ellis novel American Psycho is an example of this style of satire, in which the excess and greed of the American business culture of the 1980s is satirized through the violence and self-indulgence of the main character. Selfishness and inhumanity are portrayed in the book via the protagonist, who is a serial killer who works on Wall Street, and how other characters interact with him.
A Modest Proposal by Jonathan Swift is, perhaps, the most famous work of dark satire. In this 1729 work, Swift proposes a solution for the poor and hungry citizens of Ireland, in which they sell their children as meat to wealthy English people. This is, of course, a horrifying and repulsive prospect, and this type of satire is meant to make the reader recoil from the very idea. In this moment of disgust, however, the reader is meant to understand that the suggestion is meant as a commentary on the apathy of the wealthy toward the poor, and the desperate measures people may take to survive.