Captain Kirk would be proud of me

Grandboy: You’d never lie, would you, gwumpa?
Me: What if I told you I ALWAYS lied? Would you believe me then?
Grandboy: Of course I would!
Me: But then you’d have to believe I’m lying.
Grandboy: …yea… (wheels start moving)
Me: But if I always lied, you couldn’t believe what I said, which was actually the truth.
Grandboy: Just DON’T LIE GWUMPA, DON’T DO IT. IT HURTS MY BRAIN