What’s more, the guy said he HAD brown hair, which is true. He had brown hair. When he was 15. (Technically, he probably still does on some parts of his body) There’s not really a good term for this kind of thing, but might I suggest a “Lawyer’s Truth?”
Technically, a lie is an intentional untruth. Lying is the act of intending to deceive. It’s entirely possible to deliver a lie in good faith, in which case the lie belongs to whoever convinced the speaker originally.
‘Untruth’, in this context, means something the speaker doesn’t believe is true. Note that people can believe some pretty absurd things. And, sad as it makes me to admit, a lack of intellectual honesty doesn’t usually qualify as a lie, it just makes the speaker an unreliable source.
Deliberate lack of intellectual honesty is a different matter, of course. If a scientist isn’t honest about the results of his experiment, he’s lying, because he’s actively presenting it as evidence for his conclusion. Even if he truly believes his hypothesis. Even if his hypothesis is later proven true. (Yes, Einstein, that was directed at you)
Claiming knowledge of something is without any evidence one way or another, in an deliberate attempt to manipulate someone (some writer was trying to present this as the technical definition of ‘bullshiting’ a few years ago) is lying.
Claiming knowledge of something on evidence that no one else can measure is not, in and of itself. It’s often (but not always) intellectually dishonest. It often leads to actual lying, though, if you’re not up-front about where the belief came from.
More casually, a lie is any intentional deception, weather it involves telling technical lies, or not. In casual conversation, the brown hair guy was lying, as he was deliberately misleading about his appearance.
Casual conversation being defined as ‘any conversation where you wouldn’t spell out “he was technically telling the truth, in a misleading fasion.”
I don’t see a significant moral difference between actively lying and presenting the truth in a deliberately deceptive way.
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There are so many ways to be deceptive. No two are quite the same, like snowflakes. Also like snowflakes, they cover up most of the potholes in the path of life, and it’s easy to slip on them and break your neck, in metaphorical or literal fashion. That’s why we need the bitter rock salt of intellectual honesty. But that’s bad for the plant life of hope, and the small, furry animals of romance, and the water-table of getting laid and/or elected. Many areas have now switched to the gritty sand of willful self-delusion.