Lying almost always causes harm. The only exception to this is if the questioner has forfeited his right to the truth because of his evil intentions (much like the difference between murder and killing in self defense).
In 99.9% of situations in life, someone’s life or physical well being is not at stake. Thus a lie does indeed cause harm because it erodes our trust between one another. Society requires a certain level of trust between individuals in order to function optimally. When there is little to no trust then relationships deteriorate, cooperation becomes difficult and society begins to stumble rather than thrive.
There is also no way to anticipate the effects of a lie. We can think there will be no harm done, but that is impossible to truly know. Once lies become known the teller’s reputation is damaged, and what if at a later time that individual needs to have his word trusted because of an important matter? His lies have then harmed not only himself but whatever important matter he is now trying to help.
In short, lies almost always cause harm and cannot be justified.
