Madness (or Insanity) is a word that can have different meanings:
- Up to about the 19th century someone who acted strangely, or outside the socially accepted norms was called mad or insane. This could range from having weird ideas to someone having delusions or hallucinations, as they are common in some mental illnesses, such as psychosis.
- Today, those having delusions or hallucinations (or other mental illnesses) are sometimes called mad or insane by people who are not doctors. Doctors say they have "mental disorders"
- Certain diseases, such as rabies, lead to a major change in behaviour. An animal that suffers from rabies is sometimes called rabid or mad.
Being able to tell right from wrong is the base of a working society and of law; for this reason, the law treats those people differently who are not able to make this distinction. In the law, when people who can’t understand that their crimes are crimes it’s called the insanity defense.