“In my experience, the truth is usually in between the two stories.”
How many times have you heard someone use this line? I’ve lost count. It’s an awfully convenient line, allowing the speaker to sound sophisticated and wise while also providing an excuse not to investigate the matter.
It’s nonsense.
“The truth” is simply a name for what really happened. It doesn’t move around as more people speak. It’s not a weighted moving average. It’s what actually went down in the real world, and the truth itself never alters no matter how many false statements are made. In my experience — and I suspect in that of most others, really — it’s extremely common for one version of events to be much, much closer to the truth than another is. Only investigation will let us determine where the truth lies.
If no real investigation is possible, it may make sense to assume the truth is somewhere vaguely in between the two versions. If there is genuinely no other evidence and no hope of acquiring any, what else can the evaluator do? The only options are to do nothing at all, to choose between them based on the evaluator’s own prejudices, or to assume approximately equal credibility. Someone might legitimately choose that last option when no better choices are available.
More often, though, it’s a statement born of laziness. The speaker just doesn’t want to be bothered determining the truth, so assumes it to be somewhere near a sort of compromise. Unless some other party is supervising, there’s no downside for the person taking this shortcut … but there sure is for the truthteller.