A dilemma (Greek δίλημμα "double proposition") is a problem offering at least two solutions or possibilities, of which none are practically acceptable. One in this position has been traditionally described as "being on the horns of a dilemma", neither horn being comfortable, "between Scylla and Charybdis"; or "being between a rock and a hard place", since both objects or metaphorical choices are rough.
The dilemma is sometimes used as a rhetorical device, in the form "you must accept either A, or B"; here A and B would be propositions each leading to some further conclusion. Applied in this way, it may be a fallacy, a false dichotomy.
In formal logic, the definition of a dilemma differs markedly from everyday usage. Two options are still present, but choosing between them is immaterial because they both imply the same conclusion. Symbolically expressed thus:
Which can be translated informally as "one (or both) of A or B is known to be true, but they both imply C, so regardless of the truth values of A and B we can conclude C."
Horned dilemmas can present more than two choices. The number of choices of Horned dilemmas can be used in their alternative names, such as twopronged (twohorned) or dilemma proper , or threepronged (threehorned) or trilemma, and so on.
Constructive dilemmas
Destructive dilemmas
