Very thoughtful comments under the initial post. I was thinking somewhat along those lines, but people put things quite well. As a dialogue I will put forward a difficulty that had originally occurred to me. To say something encouraging that is not a known truth, or not yet, is something for another person's good. This seems very sensible as a way of helping to win a war pr win a championship or endure a hardship, because we are social creatures who do not stand alone but respond to encouragement from our fellow humans. That someone else "believes" we can make it through can help us believe it as well, and make it true. That seems quite legitimate, and would not qualify as a lie, in my book. I suppose if it is something that is an oversell, so that we are encouraging someone to attempt something that can only end in failure it might not be so permitted. I am thinking of the ridiculous and I think damaging encouragement children are given these days to "Follow Their Dream," as if the only thing preventing them frombecoming Queen of the May is a lack of confidence. You gotta believe.
But is it not necessary in war to discourage an opponent? On the lesser level of athletic competition I have never approved of those psych-out moves meant to intimidate, but those are entirely accepted in current culture. That is not a positive use, but a negative one. Yet that also cannot be the correct dividing line, because "giving aid and comfort to the enemy" is recognised as treasonous, as is discouraging one's own troops - though it happens these days quite readily when the war in question is seen as belonging to the other political party. I used to find it infuriating to hear not only journalists and opinion-makers, but elected officials wonder "how long will America put up with this?" only a few weeks after we had started in Afghanistan and Iraq. So whether one is trying to encourage or discourage others is not the key. Are we down to it simply being whether we are telling a sort of lie for a good cause or a bad one? And if so, what sort?