Suppose that tomorrow when you step out of your home that an alien spacecraft lands in front of you. Several alien beings get out of the craft, point at you, laugh, get back into their ship and leave. Now suppose that this is no hallucination, no dream; it really happens. You are now the possessor of implausible truth. What chance do you think you have of convincing anyone else of what happened? You have the truth, but no one will believe you.