What is truth? Can you hold it in your hands? Smell it? Taste it?
The problem is in defining what is true. It's a philosophical problem that has no clear answer, but what we do know about the world is that truth is based on authority.
Why? Because I said so.
Don't agree? Why not? Because you say so, or, because someone else says so?
And then you get into other philosophical problems regarding truth, at least as far back as the ancient Greek civilization: The move "The Matrix" as an idea can be traced back to "Plato's cave".
So who do you trust? Who is your authority for what is true? And what constitutes proof for something that is true, if your proof is being manipulated, like in "The Matrix"?
Is the abyss staring back at us? Does a tree make a sound when it falls if no one is around to hear it? How do I know you're not all just well-written computer programs designed to interact with me, to keep me busy and away from the truth?
We say we know what the truth is, but the truth makes liars of us all in the end, because we can't even prove we exist to anyone else but ourselves.