Has there ever been anywhere a law criminalizing certain thoughts? The closest I can find is The Treason Act 1351, which is still in force in Britain today. This criminalizes compassing or imagining the death of the King. The statute goes on, however, to say that it is necessary that the offender be 'attainted of open Deed', so this is not a pure thought crime.
I am not counting the laws of religious bodies, just the laws of states.
There are certainly situations where your thoughts turn something into a crime or not. Here's an interesting one (found when I tried to figure out what an "attempted crime" is):
Let's say I give up my business and sell a lot of office equipment very cheap. You think that because it is cheap, it must be stolen, and you decide to buy some of my what you think are stolen goods. You are now guilty of an attempt to buy stolen goods (even though the goods are not stolen at all, that's why it's only attempted). Someone else who buys some items because they are cheap is not guilty. So your thoughts turn this into a crime (obviously close to impossible to prove unless you tell someone about your thoughts).
Whether you want to call this a thought crime or not is up to you.
[uk]
The Treason Felony Act 1848 section 3 makes it a crime to "imagine, invent, devise, or intend to deprive or depose our Most Gracious Lady the Queen, from the style, honour, or royal name of the imperial crown of the United Kingdom". One found guilty of such an imagination is "liable to be transported beyond the seas for the term or his or her natural life", though "Reference to transportation for life to be construed as reference to imprisonment for life or any shorter term".
It is worth noting that the act has not been deployed in a prosecution since 1879, and in a legal challenge to this law Lord Steyn said: "The part of s3 of the 1848 Act which appears to criminalise the advocacy of republicanism is a relic of a bygone age, and does not fit into the fabric of our modern legal system. The idea that s3 could survive scrutiny under the Human Rights Act is unreal." However that case failled to change the Treason act, and the there is an effort to repeal the Human Rights Act, though that is not going so well.
