Montesquieu

A cer­tain Marsyas drea­med he cut the throat of Dionysius.1 Dionysius had him put to death, saying that he would not have dreamt it by night if he had not thought about it by day. That was a great act of tyranny ; for even had he thought about it, he had made no attempt.2 The func­tion of laws is to punish only overt acts.

Plutarch, Life of Dionysius.

The thought must be connected to some sort of act.