"I can also, however, commit a falsiloquium, when my intent is to hide
my intentions from the other, and he can also presume that I shall do so,
since his own purpose is to make a wrongful use of the truth. If an enemy,
for example, takes me by the throat and demands to know where my
money is kept, I can hide the information here, since he means to misuse
the truth. That is still no mendacium for the other knows that I shall
withhold the information, and that he also has no right whatever to de-
mand the truth from me...
Not every untruth is a lie; it is so only if there is an express declaration of my willingness to inform the other of my thought. Every lie is objectionable and deserving of contempt, for once we declare that we are telling the other our thoughts..."
From his Lectures on Ethics, p.203