One thing that being a scientist has taught me is that you can never be certain about anything. You never know the truth. You can only approach it and hope to get a bit nearer to it each time. You iterate towards the truth. You don't know it.
I once went to one of those parties where everyone throws their car keys into the middle of the room. I don't know who got my moped but I drove that Peugeot for years.
