From Lying/Denying - R. Doody - MIT

Quick Aside: can a lie be true?

There's a worry that clause (b) is too weak. It should be revised to require not
only that S believe p to be false, but also that S truly believe p to be false. You
cannot truly lie if you're telling the truth (even if only by accident). Or so the
worry goes.

I am inclined, however, to think that clause (b) is in fact too strong. Less is
required to lie than (b) allows. Here's an example.

Roger's Coin Flip. Roger is going to flip his lucky fair coin. He
will flip it in the privacy of his office, and the report the result to
the rest of us. It is going to be quite the event! Sadly for you, you
cannot make it. Later, you bump into me on the street. You falsely
(but reasonably) believe that I had been there for the big reveal.
(Unbeknownst to you, I wasn't there either). You ask me, "How
did Roger's coin land?" I respond, confidently, "It landed heads."
As it happens, the coin in fact did land heads.

It seems fairly clear to me that I've lied to you --- even though what I've said
happens to be true. The problem is that I have no good reason to think the coin
landed heads. I wasn't there. Moreover, I know the coin is fair. So I also don't
believe it's false that the coin landed heads either. In order for a lie to be a lie, it
needn't be false and, contra clause (b), the liar needn't believe it to be false.

You might think, in fact, that the liar needn't properly disbelieve the lie in order
for it count as a lie even! Amend the above case so that we all know that Roger's
lucky coin is, say, biased 90% toward heads. So I am fairly confident, despite
not being there for the big reveal, that the coin did in fact land heads. Still, I
lied to you. (This perhaps provides some support for the view that knowledge,
and not just mere true belief, is the norm of assertion.)

There is potentially a puzzle here. Even if I know antecedently that the coin
was likely to land heads, if I wasn't there to witness it, my assertion is a lie.
Suppose that I was there for the big reveal. And that, due to the effects of
the unrelenting ravages of time on his eyesight, Roger's ability to determine
the outcomes of coin toss is compromised --- making him only 90% reliable at
accurately reporting such things. If my confidence that the coin landed heads
is based on Roger's testimony, then my assertion is not a lie. (Or so it seems to
me). What's the difference?