I think that one of the most effective ways of lying is by couching a lie in the truth. I think people do this rather a lot - sometimes consciously, often unconsciously and it can be very pernicious. Let me explain with a trivial example from the beautiful game.
I love football. I love playing it, I love watching it and I love talking about it. In general though, I don't like commentators. Most of them annoy me, many of them say the most ridiculous things. The one that's bugging me at the moment is one that you hear very often. Picture the scene, a striker has just had a opportunity and shot wide, the commentator then states: (and you can almost hear the head shaking that goes with it) "You've got to hit the target to score" This is a really good example of a lie disguised by a truth.
What the commentator is doing is being stupid. They don't realise they are lying but they are using a truth to sell a lie. Clearly, without doubt, when you shoot in football, in order to score, you have to shoot between the posts - you have to hit the target. Hence the statement is logically and demonstrably true. However that's not what they are actually saying. What they are saying is more than that - they are saying that the striker got it wrong and has failed in his job (which is to score). I would maintain that this is nonsense. In order to score you need to do a bit more than that - let us for the sake of argument define the strikers job as He must maximise his chances of scoring.
Now, imagine a striker about 18 yards out. Every professional footballer could take 100 shots from that position and aim them at the goal and hit the target almost every time if that was their only aim. So, let us conclude that 98 of the 100 shots would be on-target. Of those 98 shots I would speculate that a goalkeeper would save 95 of them. Because any shot that is guaranteed to hit the target is likely to be close to the goalkeeper. So in our theoretical situation the striker scores 3% of the time. Another striker is in the same position but now instead of aiming just for the goal, he aims for the corner of the goal - one or other of them. (It may interest you that premiership teams have training regimens that focus on shooting for the corners). Of his 100 shots probably only 60 will be on target - 40% of the time he will shoot wide. However of those 60, the goalkeeper will probably only save half of them. So he will score 30% of the time. In one situation every shot pretty much is on target but the scoring rate is 3%, in the other, almost half of the shots go wide but the scoring rate is 10 times higher. So when the commentator says "you've got to hit the target" he's wrong what he should say is "you need to aim for the corners...knowing that sometimes you'll shoot wide but...."
So why does this matter? Well, let's be honest, in football it really doesn't. However there are other areas of life where it really does. I have known lots of people who have been recently bereaved be told "Time is a great healer." There is a great lie that sneaks in by using a truthful statement. Communication is never about what we say but always about what the other person hears. To some extent we control that, to some extent we don't. When we say "Time heals" what we usually mean is that "things will get better and it won't always hurt this much." What we actually say and what is often heard is "Your pain isn't really real because it will feel better in time." The other thing is that time doesn't just heal. It's a long and painful road to come out the other side of grief and denying that is so dangerous. It's a lie that slips in by using a truth. The best lies often do.
As someone very wise once said: "The truth will set you free..."