> Well said, Cephalus, I replied; but as concerning justice, what is it? --to speak the truth and to pay your debts --no more than this? And even to this are there not exceptions? Suppose that a friend when in his right mind has deposited arms with me and he asks for them when he is not in his right mind, ought I to give them back to him? No one would say that I ought or that I should be right in doing so, any more than they would say that I ought always to speak the truth to one who is in his condition.

Intent very much matters. It's right there at the beginning of the reading on the topic. (The Republic, Book I)