A thoughtcrime is an Orwellian neologism used to describe an illegal thought. The term has also been used to describe some theological concepts such as disbelief or idolatry, or a rejection of strong philosophical or social principles.
The term was popularized in the dystopian novel Nineteen Eighty-Four by George Orwell, wherein thoughtcrime is the criminal act of holding unspoken beliefs or doubts that oppose or question the ruling party. In the book, the government attempts to control not only the speech and actions, but also the thoughts of its subjects. To entertain unacceptable thoughts is known as crimethink in Newspeak, the ideologically purified dialect of the party. "Crimestop" is a way to avoid crimethink by immediately purging dangerous thoughts from the mind.
Some modern publishers have described people who were being prosecuted and burned at the stake for heresy in various countries that followed Abrahamic religions, as being victims of thoughtcrime laws. Such victims of thoughtcrime laws would sometimes be offered the chance to repent for their thoughtcrimes.
People were similarly executed, or imprisoned in concentration camps, for thoughtcrime during the 20th century in totalitarian regimes, such as Stalinist USSR, Maoist China, and Cambodia under the Khmer Rouge.
The word is also used in instances where people are prevented from voicing opinions which are politically incorrect or which others may potentially be offended by. This prevention may affect speech, writing, and other forms of expression.
The Thought Police (thinkpol in Newspeak) are the secret police of the novel Nineteen Eighty-Four. It is their job to uncover and punish thoughtcrime. The Thought Police use surveillance and psychological monitoring to find and eliminate members of society who challenge the party's authority and ideology.